Yeah, i agree with zeus. For example a question answer site:
If the site is well optimized for google, then the googler will find your page with the question he/she was looking for, and after reading the answer he/she will leave. If that page does not give good info then he/she will start searching for a better question on that page:
So if he/she leaves means: good page
if he /she start to search for other similar questions: bad page...
There are other profile sites, like zeus mentioned, which can be looked good besides a high exit rate.