Depending on your permissions and if you would let it know about Facebook events, calendar events, etc. then you might get notifications or see when someone is going to be going to the same restaurant, etc. I think events is the key, while you're focused a bit on city. They do specify event so that's something, perhaps.
The thing that feels different between now and Web 2 is that the Internet is so much bigger. So you can build an app that has a niche and it can still be pretty big. I was on the early beta for this app and it's great, especially if networking and travel are a big part of your life. I honestly have no idea if it even needs to be bigger than that although I know it can be.
But they shot themselves in the foot by trying to become Yelp and moving Foursquare into “Swarm”.
Their problem was they couldn’t come up with a monetization strategy that was working and at the same time Yelp was raking in the valuations.