Thank you, Rob, I appreciate your comments. I do not discount the value of Foursquare -- it has definitely revolutionized the way we interact with the retailers, restaurants, services, and establishments around us. Foursquare has clearly trailblazed the concept of checking in -- hands down.
It's just that I think it needs more in order for it to compete for our time and attention. That's where Yelp comes in.
Oddly enough, I was thinking: hmm, can't there be one 'syndicated' check-in service, whereby I can check in through Foursquare, Gowalla, Loopt, Yelp, and Google+ all at once? With such a service, I can leave a tip and snap a photo -- and my content would be shared among several networks, much like creating a message on HootSuite or TweetDeck can be published simultaneously. If you find out about something that aggregates the check-in experience, let me know.