It's not that often that I think there is something really smart coming around that will be the next big thing. But when it comes to Foursquare I said this from the first day I saw it, some months back, long before they have been active in any city I am normally in. So I signed up pretending I was in Amsterdam. Then I moved virtually to Berlin - and some weeks ago it finally came to Hamburg and other cities I visit more often.
Just to tell you: I am convinced that Foursquare will be the next big thing. There are some more localizing services like Gowalla - that e.g. some of my German friends like better than Foursquare - but imho 4sq (as its shorturl on twitter is) is today not only the by far best but in trend setting cities by far most popular service.
Some things about 4sq in this interview with the founder:
Why am I convinced it will fly - and why am I as a digital communications strategist so excited about it?
Just because it's so damn easy to use and so much fun - and because they have a smart business model that is extremely attractive for a lot of businesses: You can target and offer special offers to people that are just around the corner of your shop, restaurant or any other venue.
You can bring people to play and compete and to become "Mayor" (visit a place more often than anyone else) of your venue, the first shops have special discounts for Mayors or battles. Just see the battle that is going on between a colleague and me on who will be mayor of our office (I will beat her, b/c she is on holiday now, ha!). Think about what will be possible next year.
One cute example from Germany - and I have to admit: chapeau for bringing the first client to forquare to the executing agency - is right now Vodafone. Take a look at the Hamburg example, they do this in some other cities as well.
I would not call 4sq kind of "Twitter 2.0" - but a real smart social game and business tool that uses twitter (and other realtime web services) to get some speed. As I use to say: It's not about twitter as a company or service but as a new infrastructure for social interacting. Fourquare is just the first hot example of how to use this new layer of communications for something cool, that works.