All of this stuff is horridly out of sync with the digital age. There should be something like Itunes where you can purchase a license to post a cover song on YouTube for 99 cents or hell $2-3. That would generate millions of dollars in revenue for the industry.
Yes Limelight is kind of helping things, but while $15 is totally reasonable for a mechanical license, the average person who just wants to post a video of them singing a song on YouTube for no commercial purposes whatsoever isn't going to pay that.