Here is an interesting article I recently found:

Hackers using fake YouTube pages to attack computers on yahoo.
http://ca.news.yahoo.com/s/afp/081010/technology/us_it_internet_crime_youtube

Brief overview:
SAN FRANCISCO (AFP) - Computer security specialists warn that hackers are using fake YouTube pages to trick people into opening their machines to diabolical software.
 
A deceptive YouTube attack evolving as it spreads on the Internet is part of a growing trend of hackers to prowl popular online social networking communities in which people trustingly share web links and mini-programs.



This figures, and actually I'm surprised that this hasn't actually happend sooner. Considering youtube has been around for a while now, and they get millions of visitors a day and serve up youtube videos to millions of sites per day.