Did you check in today on Foursquare? How about Facebook Places? Gowalla?
For me, "checking in" is a part of pretty much my daily routine. I love seeing where my friends and colleagues are checking in, I love all the "badges" and gaming aspects of it, and, of course, I love the specials that many places are now (finally) offering for those of us who check in.
Checking in is becoming more and more popular.