I've done a fair amount of work on trying to detect and deal with spammers, fraudulent activity and such. Nothing beats a human eye.
My most successful approach has been to filter out the super obvious stuff, then send the rest to a queue that is kept an eye on by humans. A small staff can easily fight back against bullshit. Yes, YouTube is orders of magnitude above what I've dealt with, but I'm sure their smart engineers can filter out the majority of stuff.
It's painfully obvious that YouTube lacks human eyes on things. That, or they lack direction and empowerment of their employees.