According to a study by DLA Piper, one third of employers have disciplined employees for something posted on a social media site.
(In addition, 21% of employers had to give their employees a warning for posting something derogatory about a colleague or about the business itself on their Facebook, Twitter or Google Plus account. Of course if I posted something derogatory about myself, I would have to discipline myself. No gummy bears for a week maybe?)
Source: Britopian