How do you get 4 million YouTube views of your new song? Use profanity in the title and the song, and post a video of it.
The one thing that Cee Lo (half of the Gnarls Barkley group) did do which was clever is that he posted the full version of the video on Facebook, but made you "Like" his Facebook page in order to view it. That is a good example of giving away some content for free, and then requiring something to get the more advanced content.
Warning. These videos are not safe for work.
Original Cee Lo F--k You Video
New / Final / Official Cee Lo Video (This is the one you originally had to "Like" his page on Facebook to see.)
Source: Entertainment Weekly via Matthew Stein
Update: Here is an awesome response video sent to me by Eric Vreeland