Mobile networks going down under extreme load is an established phenomenon, but less well-known is the fact that the authorities in many countries strategically take down the mobile network for security reasons when it suits them. I was in Nigeria during the 2003 elections, and the authorities, worried about a possible coup and other organised problems, turned off the mobile network on election day. I seem to recall it was a Sunday, and as there was also a curfew and limit on road traffic, not being able to speak to anyone in a country with barely any landlines was a real problem.

Here in London there is considerable opposition to mobile phone access on the underground, mainly due to noise issues. In a society with far more mobile phones than people (I know people have three active handsets), it's already a problem to hear yourself think on an overground train journey. The internet is a completely different proposition, but mobile internet still has a long way to go yet before it's a reasonable proposition.