At the 2012 Olympics in London, two athletes were expelled for offensive tweets on Twitter(1).
Are there social media guidelines for athletes in the Olympics? If so, are these enforced by the IOC, international sport federations, or national teams?
There are guidelines for social media which is enforced by the IOC. Basically they are encouraged to use social media to post or tweet photos etc as long as;
any such postings, blogs or tweets must be in a first-person, diary-type format
Also they can't use their social media to promote sponsorships or advertisements.
This next quote is probably the most important and interesting part of it as it seems to be the downfall of most footballers when they tweet!
Postings, blogs and tweets should at all times conform to the Olympic spirit and fundamental principles of Olympism as contained in the Olympic Charter, be dignified and in good taste, and should not be discriminatory, offensive, hateful, defamatory or otherwise illegal and shall not contain vulgar or obscene words or images.