There's a process that takes place before you "get sued". If someone posts a video of one of my songs on YT without a license/permission, they get sent what's called a take-down notice. Pretty obvious what that is, it's a notice that you've posted copyrighted material and you need to take it down. If you comply, and remove the video, there's no problem and that's where it ends.

If, on the other hand, you don't remove it, and if you were to have a substantial number of infringing videos posted, you start running the risk of getting sued...especially if the copyrights violated are owned by labels or publishers who keep an eye on that sort of thing.

The specific laws regarding take-downs, infringements, etc. vary from country to country. In the U.S., the process I described is what typically takes place. I've sent, or had someone else send, a few take-down notices. There is some of my stuff on YT that, while technically is infringing, I view as harmless and innocent and I don't worry about those. It's only if I see someone profiting from the infringed works that I get proactive about making it stop. Hope this is helpful to the discussion.

*by the way, you can do a search for "youtube takedown notice" and you'll find a page that describes the process.*

http://www.rogerbrownsongs.com
http://www.nashvillesongwriters.com/roger-brown