Still, I do think there's merit in keeping your personal life to yourself and not telling your coworkers more than they need to know. I'm not saying you should be stoic or a dick or anything; by all means engage in conversations and be nice. I'm just saying that it's important to have boundaries.
I tend to be someone who overshares a lot (hence my enormous word count on Hacker News), so I just try and keep this in mind.