It was reported quite widely last week that there will be more troops covering the Olympics than are currently deployed in Afghanistan. Please note I do not support TheTruth's conspiracy wierdness.
You do have to ask yourself how, as a nation, how on earth we have got ourselves into a situation where we need 12000 army personnel, roof top missile systems and air force and navy support (as well as airport style security for punters) to stage a bloody sports tournament. No other Recent Olympics or football tournaments have required this level of security.
I guess we are more of a target because of our actions in Iraq/Afghanistan so why take the risk? The kudos to a terrorist organisation of a major attack at the Olympics would be right up there with 9/11. Personally I am happy that it will take me a little longer to gain entry to the events I am going to if it means I do not end up sitting next to some **** with a bomb in his back-pack.