Here's an interesting one. The NFL - the organisation that runs American Football in the USA - has banned its players from tweeting during games, as per its policy of banning all mobile phone use.
It's not clear what the punishment is, and it's unlikely that it's going to stop attention-seeking players from breaking the rules for the press coverage. Many high-profile NFL athletes use Twitter to communicate with their fans.
Could the FA ban football players from tweeting during a match? It doesn't seem to be an issue right now, so that's unlikely. American Football is characterised by periods of downtime, whereas our "soccer" is more of a constant action game, so it's unlikely that players would have time.
Still, half-time or penalty shoot-out tweets would be something pretty awesome. Anyone know of any UK football players tweeting during a match? Share a link in the comments.