Foursquare can be loads of fun for the casual user and collecting badges can be just as fun as trying to be the local town mayor. Foursquare has still to come up with a good tool for events, but it does have the Swarm badge.
Get 50 of your best friends to checkin at the same location at the same time - and you’ll get the Swarm badge too.
Are you using Foursquare or Gowalla? What do you think? is it a game or a marketing opportunity?