Axis of Awesome - 4 Chords on a guitar = lots of songs

I didn't realize there were so many songs that are just four chords (the same four chords). Then my friend Mark shared this youtube video with me. Check out these guys: The Axis of Awesome 4 Chords (2011) Official Music Video.wmv

So I guess once you learn one song with at least four chords on the guitar then you actually know much more than you thought you did. Keep practicing.