Louise Mensch, the Conservative MP, didn't react as perhaps the sender of the threatening email she received on Monday had hoped. She came out swinging - as anyone who knows her even a little might have been able to predict.

"Had some morons from Anonymous/LulzSec threaten my children via email. As I'm in the States, be good … to have somebody from the UK police advise me where I should forward the email," she tweeted. And then followed up by refusing to be cowed: " I'm posting it on Twitter because they threatened me telling me to get off Twitter. Hi kids! ::waves::".

Sticking two fingers up at Anonymous might have drawn some gasps a while back. (Of course, it's impossible to prove that it really came "from" Anonymous, and many Twitter accounts from members denied the idea: "1. Not discussed in IRC [Internet Relay Chat, the favoured gathering place for Anonymous members]. 2. Email & threats of violence not Anon's MO [modus operandi]. 3. @louisemensch is not important enough," tweeted one such, JohnDoeKM.) But the group is looking less like a force and more like an incoherent rabble as a result of the past two months, when many of its ideals have been washed away in a tide of misdirected hacking, which in turn has led to a number of public defections by people disaffected with its lack of focus.

Departing now

As one departing member posted on Pastebin (the favoured site for declarations relating to the group):

"Anonymous fights for freedom, you don't like people controlling you, that is admirable. But while you fight to remain free from government tyranny, you've shoved your views, into the faces of others. Because of your recent acts you've gone from liberators to terrorist dictators. I'm posting this as a guest because I feel that by simply disagreeing with you, I run a risk of attack."

And here's another (I've tweaked his Capitals For Every Word style):

So when I started with Anon I thought I was helping people but over the past few months things inside anon have changed. I am mostly talking about Antisec [an "anti-security operation being run by Anonymous] and Lulzsec. They both go against what I stand for (and what Anonymous says they stand for). Antisec has released gig after gig of innocent peoples information. For what? What did they do? Does Anon have the right to remove the anonymity of innocent people? They are always talking about peoples' right to remain anonymous, so why are they removing that right?

Or another, from "cornfog":

They jump on any possible chance they get to make headlines. Do you honestly think anonymous cares about BART... well of course they don't, why else would they release tons of personal information on innocent users who they are fighting for? Yeah... what? I don't understand this, but I don't seem to be the only one. Which leads us to our next topic, which would be Freedom Of Speech, another cause anonymous fights for.... until it's a negative comment on them, then they bash you beyond hell and harass you, and your family, for simply speaking out freely, again, something they fight for.

You get the idea: Anonymous isn't really winning hearts and minds. But the reason why not – and particularly why not in the past couple of months – is down to a group which you might have thought had taken Anonymous's ideas to a new level. That would be the hacking group LulzSec.

This was the crew gathered from within Anonymous which hacked Sony Pictures Europe, and PBS, and a number of games companies, and then raised their sights to hit the US Senate, and then the UK Serious Organised Crime Agency and finally – after saying they had disbanded – News International's site, planting a fake story claiming Rupert Murdoch was dead, and then redirecting readers of the Sun front page to their Twitter feed.

The fun may have stopped, though. In Britain three people have been arrested and two charged with offences relating to LulzSec's actions.

For some time after the UK arrests, the only visibly active member of LulzSec remained its leader, known online as "Sabu", who would simultaneously deny that he was its leader and then use phrases such as "my team". Detail about him suggested that he is Puerto Rican, living in New York and – critically – at least 30 years old. That would make him very different from the others said to be involved in LulzSec; the chat logs show that he was the mature one who directed operations. Most of Anonymous's hangers-on, who tend to range from early teens to early 20s. For almost a month after LulzSec's final hack he remained on Twitter at the @Anonymousabu account, generally either arguing with people or boosting those he backed. (For a period he seemed to share the account with at least one other person: the timings of the postings, with a "double peak" roughly correlating to one person based in Europe, and another on the east coast of the US, and the multilingual content at particular times, didn't quite tell the story of a single person. But the second "identity" went away in the past couple of weeks.)

Who's snitching on whom?

Then came a vicious chatroom dispute with Mike "Virus" Nieves, whom Sabu accused of having passed on information to the New York police following a comment he, Sabu, had made about nyc.gov. Sabu denounced Virus on Twitter as a "snitch" and began putting out details about him. Meanwhile, the "doxers" - people in the online world who like to make individuals' details public - began putting together their profiles of Sabu. The most recent ones pulled together a number of details, including photos, emails, websites and history for someone who is claimed to be Sabu. Unlike previous "unmaskings", Sabu didn't deny these ones; he simply disappeared, leaving a gnomic tweet echoing The Usual Suspects ("The greatest trick the devil ever pulled was convincing the world he did not exist. And like that... he is gone.").

He hasn't been visible online since. It's not presently known whether he has been - as they say in hacker circles - "V&". (V + "and" = vanned, or "given a ride in the party wagon": in other words, arrested.)

But Sabu's actions, while he was visible, left a vacuum in Anonymous. One prominent hacker, The Jester – reckoned to be an ex-US military member whose aims are antithetical to those of Anonymous, and who operates on his own targeting what he sees as anti-American jihadist sites (but also, when it released the US diplomatic cables, WikiLeaks) – asserted that Sabu was doing everything you'd expect of an Islamic cyber-terrorist. Most notably, targeting western government sites rather than those of Burma, Libya or China or any of a number of arguably more repressive regimes than the US or UK. Sabu denied this vehemently.

The trouble was, LulzSec's aim – to hack for laughs – didn't seem to hold up. The game had gotten serious. Which meanwhile left Anonymous wondering what the hell it was for.

Of course, the thing about Anonymous is that it isn't exactly organised, and it doesn't exactly have a manifesto; more a modus operandi, which is to use computing and networking technologies to protest at what it sees as infringements of what it sees as rights. Sometimes these are spot-on: when the members of the collective used their power to overturn attempts by the Church of Scientology to suppress discussion (and even publication) of its documents, it was definitely acting as a force for good – against repression. Some of the actions early in the Arab spring – aimed against the websites of governments trying to suppress citizens – were arguably useful (though it's hard to evaluate their real impact).

Moving out of credit

Attacking PayPal and MasterCard, though, was less smart, even if it was principled (the principle being that Anonymous likes WikiLeaks, and PayPal and MasterCard were doing things that didn't help WikiLeaks, so Anonymous would be unhelpful in return). The flaw though was that many people were recruited to allow their PCs to be used as bots in botnets targeting those sites using the LOIC software. The problem with that is that knowingly being part of a DDOS attack is against the law in the US, UK and a number of other countries; arrests followed. The FBI is reportedly working through a list of a thousand IP addresses whose owners may face arrest; so far it's still in the first hundred or so.

Further down the defensibility scale was the attack on the website of ACS:Law. The London solicitors firm had already made a bad name for itself by sending out letters to people claiming that they had illicitly downloaded music or pornographic films, and that they could avoid a costly legal case by just stumping up a few hundred pounds. ACS:Law's site collapsed under Anonymous's attack, and spilt its guts – in the form of emails and internal details. Arguably, that hastened the end of the firm by embarrassing it terribly and bringing it into the spotlight; but the speed with which it capitulated in the court cases brought against it, and that its founder Andrew Crossley had already been investigated by the Solicitors' Regulatory Authority, might have had just as much to do with it. What's also definite is that huge amounts of personal data that was leaked as a direct result of those attacks, and a significant amount was embarrassing, containing as it did ACS:Law's allegations of the names of people who had downloaded films – and the names of the films.

And similarly there was the hack by Anonymous (and including members of LulzSec) of HBGary, a US military contractor. HBGary came to the group's attention because Aaron Barr, its chief, decided to try to penetrate Anonymous (Ars Technica has the full story). it was offering to help the Bank of America, which was worried that WikiLeaks had sensitive internal documents relating to its activities during the US mortgage boom leading up to 2008.

Anonymous turned over HBGary, but nothing of any great value emerged – although there are plenty of nuggets amid the many emails, not least that there is a whole cadre of private companies in the US which are setting themselves up to provide cyber-defence – or possibly attack – to the highest bidder. (There's an excellent article on this in BusinessWeek.)

But part of that hack also involved leaking personal details of HBGary staff, and threats against them. Ugly? Yes. Avoidable? Yes: it's very simple to obfuscate contact details - it's the work of two minutes using regex to blank, say, all but the last four digits of a mobile or home number, or only the last four digits of a number. It proves that you've got it, but without the collateral damage of spreading it over the net. Certainly there's nothing to be gained from posting the full details of people who had entered competitions on the Sun's site; yet they were splattered over Pastebin.

Rules of engagement

Perhaps Anonymous needs to figure out some rules of engagement, because it's actually starting to repel some of the people who thought they liked its ideas; that's clear from what we might call the "Not so dear John Doe" letters on Pastebin.

All that seems to be left, as a result, is a few hacking crews. who seem to be of an age which doesn't yield that much wisdom: folks such as TeamPoison and his disappointing grade in Computer Science AS-level; or another (we're fairly sure) British-based hacking crew who would like to emulate LulzSec, and have spent the past week or so hacking and DDOSing (unwisely, I think) various government, police and military sites in the US and UK. (I'm not going to name them, because it only encourages them).

OK, so it's hacking, and it seems like fun, at least until the police come knocking on your door. But for Anonymous, which for a while entertained the idea that it could be so much more, the past couple of months have seemed like the downward arc from something that seemed promising to something that is just a mess. Cyberactivism? Well, perhaps if you subtract the "activism" part. As one well-publicised tweet says, you can't arrest an idea. But you can certainly corrupt it.

[Please note: comments relating to any ongoing court case in the UK could constitute contempt of court and will be removed.]

Updated: corrected chronology relating to HBGary; clarified re TeamPoison.