I mostly use LinkedIn and Twitter for professional connections, and Facebook for personal stuff.
The lines, however, are by no means clear. I have a Flickr account that’s mostly pictures of my son,
but there are some professional photo sets as well. I have two YouTube accounts, one that’s family
and one that’s professional.
I use Facebook Places, and Foursquare mostly when I’m traveling.
I’ve been known to leave a review on Yelp as well, and not just when I’m unhappy.