Copyright issues for multimedia searches are more akin to the copyright issues for Google than for kazaa. The search engines help users find the site and generally only display a small piece of a given work.
Multimedia does poses challenges. For example, SingingFish relies completely its spider. I know several artist with the same problem. They want to publish their music online, but the hungry little spiders download the files so much that the spiders alone max the site's bandwidth.
Personally, I think the best way to handle such searches would be for an industry standard way to describe media files with text. That would save the massive amounts of bandwidth consumed by multimedia spiders.