This piece expresses it well: Your tweets are always on.
For now, we are always representing our company online. It’s not quite fair, but we are always judged by what we write when we communicate (or say) and if you use any online services (blogging, social media, etc), then you could end up getting in trouble because of what you push out there.
I don’t know if it’s quite as bad as the article states, since I think you can show some separation. However you have to follow my advice and make a second account for non-work stuff. Show separation, and if you want to make political, religious, etc. comments, do it from an account that doesn’t have your employer’s name on it.