Soldiers in Iraq, dissatisfied with the limited and censored Internet service available officially, build their own. It's impressive, even though the main demand is to download filthy pictures and order foodstuffs forbidden by the chain of command - which, I suppose, gives it a sort of charm. As one of Robert Graves' comrades said, marching towards the front, Dear Mum, I am currently wading in blood up to my neck. Send fags and a lifebelt. Love and kisses.
It's probably a better idea than using a mobile phone, whether with a UK or local SIM inserted. Chez Spyblog there are details of supposed threatening calls made to the families of British soldiers in Iraq, with sceptical comment. Unfortunately, I'm much less sceptical - see this post from November 2005 on weird and clueless policy towards GSM networks in Iraq, and this one with regard to unauthorised mobile networks.
It seems nontrivial numbers of Allied soldiers are using local SIM cards provided by various networks not limited to MTS/Vodafone and Iraqna(Orascom Telecom), and these networks are possibly penetrated by the enemy. The reason for using local SIMs with GSM phones is that it is cheap. The reason not to is that all call details, locations, and numbers called are available to anyone with access to the operator's SS7 switch and databases - not just that, but the phone broadcasts its number and IMEI whenever it tries to register on the network, so jamming the real network and listening could gather identifying data.
Using Skype or a comparable peer-to-peer VoIP applicatiion from an Internet-connected computer would be far more secure - that, and making very sure no mobiles go outside the wire, as a similar method could be used to track troop movements.
On a similar Internet-politics trip, watch Charlie Stross bust my chops over IRC and the Soviet 1991 coup. Looks like I was wrong. It does mean an opportunity for an interesting anecdote, though. A Cisco Systems executive I spoke to a couple of months ago talked of selling the old BT System X digital phone exchanges to the Russians immediately post-communism. To his surprise, the first switch he visited was a 1940s all-electromechanical monster, maintained perfectly by a small army of women engineers who polished every contact, at least once a week.
There was no difficulty making the pristine copper wires do DSL, either, when he returned a few years later with Cisco. So it's probably no wonder there were IRC users in Moscow in 1991..