Did you already read this recent story about British couple sent back home by US Department for Homeland Security because of tweet made by the guy?
Be always careful what your are posting on social networks. It doesn’t matter is it Twitter or Facebook or Google+ or any other social network. It public space which can be read by anybody. Especially with privacy rules changed so frequently by these networks (Facebook is the worst on this list) any information you think is hidden can suddenly become available to millions. May be all these networks should introduce some warning system to inform you about existence of some inappropriate information in your message you are ready to post or tweet?
Share this story with your friends to make them alert.