In light of the phenomenon of the Twitter Cisco Fatty incident (if you're not familiar, the gist is that a young woman Twittered her job offer from Cisco, calling it a fatty paycheck), I feel that we need to make something abundantly clear. Twitter is very public. Sometimes, dangerously public.
Twitter is not Facebook, which while not very private itself, is more oriented toward your friends. But Twitter is a public forum. Even if you're not following or followed by strangers, you're still public. Post one buzzword, and it'll be found in a search. Not only are you at risk for relevant people finding your entry and losing something, as the Cisco fatty poster did (a job, in her case), you can also be up for public mockery, as she was.
To see what else I have to say, just read more.
I trust that my readers are smart kids who know what's good and what's not good to post on Twitter, but we all have occasional lapses in judgment and forget just how wide-reaching the website is.
My advice: Type your 140 characters, read, breathe, read again, post.
P.S. This is not to discourage celebrities from posting juicy gossip about themselves. That's entertaining.