Mmm. Even with $100 billion, I don't think they could do it at the rate people are uploading at...
There are three major problems:
1. Audio, video and image recognition systems are nowhere near close to perfect and the upload volume means even a small error rate will result in a large amount getting through.
2. Users are constantly coming up with new ways to avoid the filtering systems making it a game of tag, but where one side is made up of tens of millions of people.
3. There isn't a central registry of who owns what type of copyright in each territory so there is no good way to know if the person uploading has the right to or not.
Then there are the issues of compositions... someone has the right to a music track, but only when synchronized to a particular video or someone inserting a frame of a copyrighted image inside their video.
And this will affect far more than YouTube. Copyright extends to all creative works including this comment. Image hosting services, forums, reddit, social networking sites, comment systems, review sites should all worry.