It's almost more than my poor brain can handle, but basically, just because you purchase the right to reproduce, perform, or broadcast the song, does not mean you have the right to put the lyrics on the screen.
But that's fodder for another hub...back to the point, I don't have the right (and neither do you) to post youtube videos of friends singing karaoke. I'm happy to say it didn't take patent lawyer me long to come to my senses. The video was removed voluntarily copyright infringement photos after just three days...I didn't mention the song title, so maybe I Will Survive any potential lawsuits.