I've known about Sherdog since 2003. The HL vids brought me here, but I never ventured into the forums until around 2005. I lurked for a couple of years before finally joining. The following two reasons were why it took me so long to join:
1. This is the first forum I ever browsed, so it was kind of confusing at first (yes, I was dumb).
2. I thought that you had to pay to have an account here.
In b4 someone points out I'm a plat.
What finally made me join was the humor. There were and still are a lot of entertaining posters here. The Heavies has declined in quality, but P&M, Imo, is the best it has ever been.
This thread in particular was one of the main reasons why I joined (click the link in the post):
http://www.sherdog.net/forums/73488085-post40.html