The 90-9-1 Principle is an often discussed concept that has been used in countless conversations about online communities and social strategy. Until now, there hasn't been a single collection of description and support for the principle, making it hard to share a single links with clients, colleagues, and friends who haven't heard of 90-9-1. This site works to solve that problem!
Funnily enough, I have occasionally wanted to refer to the 90-9-1 principle, but without just hand-wavingly putting in a sourceless reference, so I had to scour the web for a good bit of text explaining things. So this site looks like it may solve an actual problem for me. This site even lists some sources, making it at least appear to be a valid and reputable theory.
Update: The web page I used until discovering this dedicated site is this one by Bradley Horowitz from February 2006. It is the earliest mention of the idea I was able to find.