Gowalla or Foursquare?

Gowalla and Foursquare are two popular services to find spots nearby and let you track your friends whereabout. You also have Waymarking from Groundspeak, the folks behind geocaching - but they do not seem to have any marked share, at least in Norway. Pushing from behind are Twitter and Facebook, as they have the users with them.

What is a marked share? I only measure it by the number of places/spots that exist when I check in and how many checkins there are. Gowalla seems to be the most popular of these two, at least in Oslo.

But how popular is this? My guess is that this, like geocaching is a niche for those with special interest in this. Until Facebook has their version ready the masses will not adopt this fun.