And loopt, brightkite, whrrl (spelling?) and probably more. And that was just within the "check into a place" category. There were also other categories like checking-in to what you're watching on tv (GetGlue), checking-in to what you're eating (Foodspotting), checking in to what you're drinking (Untappd).

Some of these are still around but most are not. Not sure if the ride-sharing space will turn out the same or not. I feel at least Uber and Lyft are probably safe.

This may be related to my provincial ignorance (I was in Ann Arbor during the check-in boom), but I remember Gowalla being the Lyft to Foursquare's Uber. Of course, there is an actual business model for the ride-sharing companies, so maybe there's room for multiple players.

It's not a great comparison because Gowalla had essentially no competitive advantage, whereas Lyft at least has the chance to have one. Gowalla competed on "better design" for a while but ultimately the network effect of Foursquare mattered far more. Lyft is making headway in some cities so I think they're doing fine.