According to news.com, the IT systems for the 2008 Olympics in Beijing will be put through rigorous testing which will take more than 1 year! The people at Atos Origin, the company in charge of setting up the IT for the 2008 Olympics, clearly know what they are doing.
It's also interesting that the article mentions insiders as a security threat -- namely, that insiders will try to print their own accreditation badges, or do it for their friends, etc. As always, the human factor is the hardest to deal with. They say they resort to extensive background checks for the 2,500 or so IT volunteers, but I somehow doubt that will be enough.