What happened to privacy?
It isn't an issue of privacy.It comes down to companies trying to protect their intellectual property. What Viacom is quite correctly getting at, is that Youtube are allowing masses of Copyrighted material to remain for free download.
Viacom isn't interested in what any one individual has watched. They are trying to prove the point that many users of Youtube and consequently Youtube itself, are guilty of Copyright infringement.
Once they have that proof they're in a strong position to take Youtube to the cleaners.
I'd like to see the same happen to Rapidshare and other filehosting sites since the majority of their content is also illegal.