A couple of days ago, I was on the phone (mobile) with an elderly relative, when the phone (land line) began to ring. I glance at it and see a number I don't recognize, Birmingham area code. Pick up. "Hello Mr Stross, I'm [XXX], calling from [mumbled company] about claiming your free—"

Now, I don't know about you, but cold-calling folks to sell them stuff is, in my view, rude. And cold-calling an ex-directory number that's in the Telephone Preference Service do-not-call list and redacted from the Electoral Register (the public version that's sold to marketers) is more than rude: it's illegal (and a clear flag for scammers). So my immediate response was a snarled "fuck off!" and a terminated call: possibly excessive, but I don't get to talk to the relative in question that often, and I don't appreciate some random jerk interrupting.

(I should have known better: cue three subsequent callbacks by $JERK, who wanted to swear at me. Well, at least I trolled him successfully ...)

What makes this call so exceptional is that there was a human being on the other end of it, and it was dialing from a UK phone line. Most phone spam these days—and despite the TPS database I get an increasing amount of it—comes from overseas, and about 50% of it is pre-recorded messages. (As I get legitimate international calls on my land line about once a year, on average, I'm considering blocking them completely; it'd solve 80% of the phone spam problem at source.) But this got me thinking.

My land line exists for one purpose: to provide ADSL internet access. The phone handset is, if anything, a living fossil—a relic of an era when things were very different. Today I barely use it. Hell, I barely use my iPhone for voice calls: it's a pocket-sized portable texting and data terminal. Voice calls are generally an annoying interruption (and getting one while I'm working in flow can kick me out of concentration for up to half an hour, badly disrupting my ability to work). Things were different 30 years ago: the telephone was a lifeline, a form of realtime social contact you could experience while isolated at home, about the only instant form of messaging most people had access to before the internet. Now, it's an intrusive annoyance, and not even terribly useful. (Just try revisiting the edited highlights of a conversation and responding to them an hour later!)

But even as the telephone has dwindled in significance in my life, telephony has gotten cheaper. Monstrously, impossibly, cheaper. A phone call requires bidirectional communication at roughly 2400 bits/second, a vanishingly tiny data rate in an age when my home has 2,000,000 bits/second of outbound bandwidth (and eight times that incoming). Voice over IP gateways are relatively cheap and easy to set up, and a £250 PC sitting on a desk can do the work of a £,250,000 branch exchange from 20 years ago.

Hence all those spammy pre-recorded messages from a PC sitting in a rack in Texas. Hence all those phone calls from Adam (in Bangalore) from Microsoft about the infection that is slowing down my PC. The biggest cost in those call centre scams is the bums in the seats: phone calls from India to the UK, which used to cost an hourly wage per minute as recently as the early 1980s, are now essentially free.

And it's going to get much, much worse, because it's a wee bit difficult to enforce local jurisdiction laws about cold-calling at five thousand miles' remove.

Consider that we now have reasonably reliable speech recognition for limited subsets of our language: if you want to recognize the words "yes", "no", "one", "two" ... "ten" (and other common digits), spoken over the phone in a variety of accents, the software to do this with 98% or better reliability is available right now, and cheap. The same bots we're used to seeing on twitter and IRC and other IM systems can in principle be speech-enabled, and come to our phones from all over the internet.

Consider that we have cheap connectivity almost everywhere on the planet—there are black spots (try phoning a supertanker crossing the Pacific and you'll rapidly discover the joys of satellite phones; try phoning Syria this week—in the middle of a civil war, the authorities having cut the lines—or North Korea), but these are essentially anomalies in a sea of bandwidth. Which means the telesales scammers are as free as the email spammers to migrate their servers to jurisdictions that give them effective immunity, or boiler-room call centre labour at £0.5/hour (for skilled, English-speaking staff).

There's no obvious way for this to end well: the inexorable downward pressure on the price of bandwidth is pricing voice calls down into spam marketing territory.

One obvious answer is whitelisting: you may configure your phone to only accept incoming calls from numbers in your address book. Or only accept calls from numbers that support Caller ID. But that's ... unsubtle. Caller ID can be spoofed. And what if your teen-age son is out late, dropped his mobile and his wallet down a storm drain, and needs to phone from a payphone or a friend's mobile to request a lift home? What if a relative is trying to call you from hospital after a car crash?

A better alternative is to let the Cloud manage the whitelisting for you. Let's imagine for a moment that Facebook is the great, benevolent, cuddly entity we'd all prefer it to be, with only our best interests at heart. FB has for some time now been pushing users to give it their phone numbers—all part of the great personal data shakedown. But consider: FB knows who your "friends" (actually, passing social contacts) are. It knows their phone numbers. And it knows, by a minor miracle of graph theory, who your friends' friends are—a wider pool—and what their phone numbers are. Being able to configure your phone to accept phone calls only from my Facebook friends— or friends-of-friends, or unblocked (available to everybody) may be the only sane way out of the telephone spam maze. And if a FoaF phones you to cold-sell you a conservatory you can report them for spamming on FB, maybe even get their account frozen (freezing them in turn out of the mobile phones of everyone who is only accepting calls from FoaFs).

I don't like this solution because it gives Facebook too damned much extra power; they are already trying to replace all email communications, and this gambit would hand them effective control over actual voice calls. Nor do I trust any of the other multinational data aggregators to do better: Google, Apple, Twitter, Klout, whoever. Turn the paradigm on its head: what would stop Facebook from allowing commercial account holders to pay for "sponsored calls", or bare-faced voice advertising via Facebook? And then turning around and offering to sell us premium accounts that don't receive advertising (yes, thank you Livejournal for pioneering that business model)?

I see no good outcome for this: and while voice telephony hasn't outlived its usefulness yet, but if we don't find a solution to the spam problem the end is in sight.