Foursquare: What can you post?

This was another question from Websites 101, Part 3 (SEO).

Foursquare lets you post comments and photos as well as checking in. Here’s the website:

http://foursquare.com/

Note that Foursquare is all about the smartphone, so you need to get the app for your iPhone, Blackberry, or Android device. So do that first!