I was reading over on APE a post about being wary about broadcasting too much in a Twitter post (a tweet for those not in the know) and on social networking sites generally.
A photographer emailed him a story about how he lost a chance to shoot a campaign with an ad agency as he put brief details about the job on his twitter page and on Facebook. Someone at the ad agency saw it and then it went down hill from there. Apparently an obscure NDA was involved...
Moral of the story is make sure you can do that with any prospective/actual work, or be somewhat oblique about what you post. That can apply to really anything, but it would suck to lose a job over something as seemingly inconsequential as a tweet.
Mike Wood Photography