The Brewers Association has released their 2012 Beer Style Guidelines. Frankly, it's a bit overwhelming and bewildering. I am an admitted craft beer fan. I like trying out new beers, and I enjoy (attempting) to speak intelligently about them. But, the guidelines by which beers are judged in the United States lists 140 unique categories of beer!
The publishers base their guidelines on historical significance, authenticity or a high profile in the current commercial beer market. Each entry includes a detailed description of the beer giving information such as ABV, aroma, appearance, along with historical notes where appropriate. All of this is of great importance to brewers and judges. For the rest of us it does provide some interesting, even if superfluous, information.
Did I mention there are 140 different styles?
See the 2012 Beer Style Guidelines for all the gory details.