I'm honestly quite surprised they got that much, seeing as they haven't really had any "huge" innovation or evolution since their original product. They have definitely improved some UI/UX on the app, but nothing ground breaking, to me. Don't get me wrong, I'm a fan of Foursquare but they are getting harder to "keep loving" when they simply can't seem to hit their full potential.

I only use the service now if a location has a check-in special of some sorts. And to get those specials, you need more adaption from local businesses and I think that is where they are failing. I live in a big city, and I think I maybe see one new business a MONTH (at most) that actually utilizes Foursquare, and majority of the time it's just a big chain type store. They need to get a team together to pitch to the smaller indie type shops to get them on board to get users interested again. I'm also in the midwest, so maybe they are better in bigger coast cities?

EDIT (additional thoughts): I think they also won the hearts of their original users with the app "game-ification" which was incredible (at the time), but I think they need more than that now-a-days. It seems like every new app has "badges", "awards", etc. While it's good that Foursquare was one of the originals by doing that in a social setting, it's irrelevant now because so many businesses are doing it better than them. Just because you created the first wheel, doesn't automatically make you the best, and I think they are forgetting that and not thinking outside of the box of how to make their app more social and connect users like it originally had.