Creepy because that's an lot of information facebook lets you look up about people pretty easily using their api. Not necessarily objecting but it is a little creepy when you think about it.

Facebook is just gathering as much information as they can so they can give it to advertisers. I don't quite understand why people have to share some of the stuff they do on facebook and find that far creepier.

I think people don't notice it until it's all presented back to them in some manner like this.

People might also have an unreasonable expectation that there's some law against misusing their data. Partly, it's because that is true in some areas, e.g. the phone company can't run speech-to-text on all your conversations and sell histograms of your word usage, so people might assume Facebook can't either.

Yea its quite creepy especially because they can get all your friends through whatever they are doing.. even with your FB account settings disallowing all websites access

What stops me (as the developer of a similar app) from screen scraping the information I gleam from visitors to my web app?

I'm not sure if that's technically possible... You'd have to get the content that's inside of the iframe, and I think that would break some sort of cross domain rule.

the security rules of browsers don't allow you to access cross domain iframe content, so it isn't an issue