[twism]

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

[cmelbye]

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.

[zachallia]

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