Mr. Answer Man says: Not necessarily. In fact, it could be a sign of maturity.
As we all well know, guys often have a hard time understanding and expressing their feelings. Scientists say that as our species developed, men learned to act first and feel later, handy when fighting mastodons but burdensome here in the new millennium. As these unfelt feelings stack up, your man begins to experience a claustrophobic anxiety that causes him to crave "space." He doesn't want to break up -- he just wants a chance to get in touch with his feelings.
Now to be fair, some guys say they need space when they trying to let a woman down easy, so here's how you tell the difference: When your guy says he needs space, let him know that's fine with you, ask him how much he thinks he'll need and if he'd be willing to commit to doing something together once he's had his fill. If he wants to break up, he won't want to commit to anything. But if he accepts those terms, what you've got is a man who's willing and able to ask for what he needs to take care of himself -- an attractive trait, wouldn't you say?