My teacher in school said that fair use http://www.copyright.gov/fls/fl102.html lets you use copyrighted work (for education, or commentary, etc...) Lets say I start a site about Paris Hilton. Can I host an image (that obv I don't have the right to) and comment on it? Or am I missing the point?
As I understand it, you would only be able to do that if you did it solely for educational purposes. You wouldn't be allowed to make any money off of it.
If your site is commercial (takes in any income via adsense, advertising, donations for bandwidth, etc) you are not going to be able to use those types of images without permission.