Copyright question

hey all — I was wondering how sites like YouTube get away with making a killing, cash wise, on user-uploaded videos etc. that are chalk full of copyritten material. For example, someone that has a video full of NBA footage, or someone that has a clip from a music video, or a boxing press conference – you name it.

I mean, is this legal? Obviously they’re not directly selling the copyritten material, but the site is clearly profiting from it.

Take the example of a “fan site” – say you have a Elton John fan site…can you just go scrapping together all the images, and videos, copy, and other content you can find related to Elton John off the net and put it together without facing legal ramifications? What if you’re not selling products, but perhaps advertising space? What if both? What if neither?

Thanks for any input,