That's a good point. But I also wouldn't call Facebook my all encompassing social identity. I don't update my status with everything I tweet; I don't even sync up Foursquare and Facebook because I don't want everyone on Facebook knowing where I've checked in (and I don't think I'm alone because 20% of Foursquare users sync up with Facebook). Many people just find it annoying, but the bigger reason is that I'm not really that 'close' with all my Facebook Friends. If I post a check-in to facebook, I'd only want a fraction of the people to know.

I haven't gotten the rollout yet but hopefully Facebook realizes this and makes Places something you can use with some of your friends, and not all of them.