Did they actually manage that transition, though? I haven't heard anyone talk about Foursquare in years. My entire social circle effectively ran itself via Dodgeball when that was active; many of us remembered it fondly enough to give Foursquare a try, after Dodgeball's founders came back out of Google purgatory. It quickly became obvious that they really just wanted to become a cheap Yelp knockoff, though, and we all left. I don't remember hearing anyone propose a group migration to Swarm at the time, and I certainly haven't heard anyone talk about it since.
Checkin-based spontaneous social organization just... doesn't happen anymore, so far as I can see. Shame, because I really enjoyed it. If a new service came along which looked like it wasn't going to be evil, I might sign up and try to get my friends on board - but I wouldn't trust the foursquare people at this point.
I just looked at my cell phone and there's a notification of 9 friends checking in on Swarm - most of them early fellow-dodgeball users.
YMMV but most of my friends who were hardcore users switched over to Swarm upon the pivot. The migration was automatic btw - Foursquare told you in the app that checkins were no longer supported and offered easy install of Swarm with the same login credentials.
Checkin-based spontaneous social organization just... doesn't happen anymore, so far as I can see. Shame, because I really enjoyed it. If a new service came along which looked like it wasn't going to be evil, I might sign up and try to get my friends on board - but I wouldn't trust the foursquare people at this point.