Interesting point and worrying for FB marketers like myself. I recently uploaded 20,000 + emails from a client (opt in so all fine there). To invite existing email subscribers using the "Tell your fans" resource. Sat back and hardly a blip. I tested this using friends and my email. I have done some research into this and many of the FB blogs and forums say this doesn't work. Apparently FB uses this data to 'suggest' your page not invite this. But are they just sucking up huge amounts of emails to use themselves?

Agree that this is a step in the right direction,one the novelty of aquiring pins wore off, but what about the quality of the content and the size of the network? My point being that Yelp.com (massive audience in comparision to Foursquare) has already done this and has a huge database of reviews (plus a nifty iPhone app for checking in.) Closer to home a very strong and conscientious community is Qype with over a 1million users (mostly in the UK). Then there is also to groovy London based Rumble to throw into the mix. What do you think?