Some really interesting comparisons to Foursquare and Twitter back in 2009 before it really reached mass adoption. Once Twitter realized that success was more than just people tweeting (but reading tweets), they took off. Foursquare CEO Dennis Crowley notes that more people are using the app, but fewer people are checking in. The reason for that? People are using the app to see where there friends are at and get recommendations. Could be pretty cool to see how the capitalize on this in the near future and make Foursquare more useful and appealing to the mainstream.