I started it in 1997 when I was in highschool. I found it interesting that slang terms frequently heard just the year before were already passe. I thought it was something that was worth capturing.
It affords me a modest salary in a fairly high-priced area, on around 2.1 million visitors a month. I estimate that it would get 2.5x - 3x the traffic (and hence the earnings) if google weren't up to strange shenanigans with the site's rankings.