Apple just recently changed their App Store it so you can only review an app if you have downloaded or purchased it. I think this is a good idea for Android Market so that there are not going to be random comments and reviews that have nothing to do with the app and drag down the star rating of good apps. If you go to youtube a lot, you know what I mean about random comments.

http://mattgemmell.com/2008/09/27/apple-is-listening