The strange case of Netshare, the application that turns the iPhone into a modem - whenever it exists - became stranger still over the weekend, when it appeared and disappeared for a second time in the iPhone App Store. Apple and AT&T (widely assumed to be the bad guy here) remained tight-lipped, leaving the world trying to figure out the significance of the strange and brief manifestations.

Once could have been a mistake, but twice? Netshare was certainly visible in the App Store during its second materialisation on Friday evening UK, where it could be purchased for £5.99 ($9.99 US, standard crap deal, don't get us started). And it works - but in operation it is a way off of the ease of use and simplicity of your dull, old-style non-3-Jesus phone hung off your Mac via Bluetooth.* That is not the fault of the software's developer, Nullriver, and it is not (entirely) the fault of AT&T or of Reg HQ's local iPhone purveyor O2. It is the fault of Apple for borking the iPhone's Bluetooth stack, and of network providers whose 'all you can eat' deals will only work so long as customers don't get into the habit of using them.

When it exists, Netshare is a "tethering" application. In situations where you can't get onto a wifi network you can create a network between your computer and your iPhone, then the computer can use the phone's data connection for Internet browsing. It's not exactly single click setup (numerous walk-throughs have been published, the MacRumors one will give you an idea), but it's something that could come in handy in circumstances where you don't have anything else.

There are other iPhone applications that do the same job as Netshare, but they require a jailbroken phone. Netshare's claim to fame is that it's the first 'official' (oh yes it is - we have the Apple receipt) app that will work with a normal handset.

In the absence of official comment from the Cupertino Curia, the various setup and use speed bumps provide one possible explanation for why the app appeared in the App Store, and why it might make future manifestations (Nullriver says it didn't violate any agreements, and is hopeful it will return). The networks (let's not just beat up AT&T) don't want great swarms of customers setting up their iPhones as wireless base stations and running their computers off them all the time, so they're agin anything that could be imagined to facilitate this.

But it's a stretch to imagine Netshare doing this - there's some hocus pocus to setup, in order to work it has to fight against several aspects of the iPhone's design (the borked Bluetooth being one of them), and hey - if you're in range of all you can eat wifi, what on earth are you doing using 3G instead? In most cases the wifi is going to be a lot faster.

So is this why it appears in the App Store? Only people who're OK about hand-tooling their network settings are likely to use it, the connection will time out or the battery will get sucked dry, and this one app is not about to bring the networks to their knees. Maybe at least somebody at Apple thinks this, but every time they post Netshare, the networks phone them up and shriek at them?

* Macs these days get on famously over Bluetooth with most mobile phones, pairing with them, syncing data with them and even browsing the web with them. Granted, the latter can involve some ferreting for scripts and incantations from the sainted Ross Barkman, but once it's set up you needn't bother even taking your phone out of your pocket. For two or three years now The Register has been using Novamedia's launch2net, which for money, does the incantations for you most efficiently.

The maiming of the iPhone's Bluetooth, on the other hand, is so blatantly cynical it's almost funny. Try to Bluetooth pair an iPhone with a Mac and you'll get a message saying, effectively, 'nothing going on with this device mate, I'd give up if I were you.' For everybody else's phone, wireless syncing, for the iPhone, it's a cable with the iPhone at one end and the iTunes store trying to suck up your money at other. Go figure. ®