The Star Tribune published an article on 10/08/08 stating that links to YouTube videos that you receive in an email could take you to a malicious web site when the link is clicked. Read the following article for details: STAR-TRIBUNE: Criminals building fake YouTube pages to spread viruses
A program circulating online helps hackers build those fake pages. Users who follow an e-mail pointing them to one of the pages would see an error message that claims the video they want won't play without installing new software first. That error message includes a link the hacker has provided to a malicious program, which delivers a virus.