You have to love when Facebook comes out with a new goodie. Well Facebook Places is facebook's version of Fourspaces. You might want to check your setting and adjust them to how you feel you want (if you want to play or not):

Go To Account > Privacy Settings > Custom Settings

Now your going to want to "Choose your Privacy Settings"

Scroll down to "Things others share"

From there you can decide it you want to play or not. Keep your friends from being able to check you in with them by disabling "Friends can check me in to places." Your friends might be annoyed with your decision, but remember this it is your privacy. You can still be tagged in status updates, however.

This one is tricky and took a few clicks to find. Scroll to the bottom of the privacy page, and under "Applications and websites," edit "Info accessible to your friends" so that "Current location" and "Places I've visited" are not checked off. This will ensure that your information is not shared with any of the applications, games and websites that you and your friends might use.