Facebook group

I've decided to use the powers of facebook to get people interested in my cartoons, I created the "I like Lee Washington's cartoon's" group here:
I like Lee Washington's cartoons

The idea being that when someone joins, it tells their friends. It's be fairly successful(although most members are my friends!) However, taffic to my website has increased, so I'm guessing that even people don't join the group, they're looking at my stuff.