ALSO...I have sometimes tweeted too much revealing that I wasn't really working that hard...haha...Sometimes you don't want people knowing what you are up to.
I don't have school issues, but it's a similar problem with having coworkers or family on Twitter. I feel that I can't vent as easily as I use to. I can't freely complain without fear of someone understanding better. There has also been minor issues of tension if post something people don't agree with that I'd rather not discuss in the workplace.
I don't usually have problems with tweeting what I whant,, except when there's a deadline on a project or something, then I don't tweet at all :p