I use Foursquare. But, mainly, oddly, for myself. I like to know where I go and how often. For example, I spent 8 days in Vegas a couple years back and can't recall the name of a single club I went to. I want that to change. So, when I went to San Fran this summer, I made sure I checked into most of the places I visited so I can look back and be like "yeah, I was there and I liked it".