Meantime, I checked in at the San Francisco airport, waited a while and checked in at a BART station downtown, then "had lunch" at a spot Cori and I went to a couple of times on my visits. It's a shame I wasn't actually there; I heard that afternoon from an IDG writer who wanted comments from me for a story, and his office is about two blocks away.
And, I checked in at the Detroit airport, at the AirRide shuttle stop, and then at the transit center in Ann Arbor. I was going to check in at the University of Michigan hockey arena next, but the transit center was what my friend Ed noticed. He freaked out and asked what I was doing a few blocks from him, then skimmed my history and discovered the interspersed check-ins in Boston and San Francisco. Otherwise, I'd have had him for more than five seconds!
There were a couple of other cities I was contemplating "showing up" in, and would probably have caught a few more folks who thought I was really nearby, but this was exhausting enough!
Last year's Foursquare prank was much simpler. I Photoshopped a Dinosaur Bar-B-Que sign onto a photo I had of a closed restaurant in Ithaca's west end, and checked in at a "new" Dinosaur location there. (Dinosaur is a chain of outstanding BBQ restaurants in several New York cities... but not in ours.) And, I shared the check-in, with the photo, on Twitter. That one got quite a few folks!