Dodgeball/Foursquare is the canonical example. dens is relentless. (dodgeball wasn't so much a failure, but was a smaller success than 4sq to date)
I hope the things I did/failed at during dotcom (a datahaven beyond the reach of nation-states, and electronic cash) end up being things I can do successfully in the future.
Great example. demonstrates the fact that if you keep solving problems in one domain / area, one day you will solve a really painful problem profitably
Maybe -- it's not clear that 4sq is a winner, but if there were any single person who I would bet on coming up with a profitable mobile location service, it would be him. If not 4sq, whatever he does next.
As far as I can tell, Foursquare has basically pivoted to become a Yelp competitor. I was excited about it initially because I thought they were going to do cool things to enable real-world socialization, but there's really none of that now. It's all about the places, not the people.
It's going to take a completely new approach to make location-based social networking a world changer like Facebook was.
