The IOC owns all the Olympic athletes and volunteers apparently

It's not like there are any trade secrets lying about where athletes can do damage merely by talking, it's just about making the most money while avoiding the most lawsuits.

From CBC News:

According to the IOC 2012 guidelines, volunteers and athletes are allowed to use social media websites like Twitter and Facebook. However, any comments or postings must be in a "first-person, diary-type format" and not come close to emulating the "role of a journalist" by commenting on separate events.
In any of their postings, they must also avoid mentioning:

• Details of their specific location,
• Media of backstage areas
• Breaking news
• Information about participants
• Detailed online discussions

There's more:

Personal photographs can posted to these sites, but cannot be commercially distributed elsewhere. A caveat to this is that any pictures taken in the Olympic Village must be vetted first by those pictured.

Videos can be shot but cannot be posted online or elsewhere in any form. Once in the stadium, only official sponsors are allowed to take video and still shots.

I guess it's good I'm no Olympic athlete, otherwise I'd be a walking broadcast network--spilling the beans on top secret stuff like the weather, the Russians' chances of winning, and what everyone had for lunch.

It's sad really: Citizen-journalists are encouraged by social media and the internet in general today; athlete-journalists are another story.