The bill that was introduced (
http://thomas.loc.gov/cgi-bin/query/z?c111:S.3339:) changed the number of barrels that could be produced from 2 million to 6 million in order to be considered a "small producer". This is largely a matter of taxation since small producers pay less than their megaconglomerate counterparts.
The Brewers Association considers crafts brewers as such: "An American craft brewer is defined as small and independent. Their annual production is 6 million barrels of beer or less and no more than 25 percent of the craft brewery is owned or controlled by an alcoholic beverage industry member who is not themselves a craft brewer." The small definition comes from the definition of a small producer.
Where it gets fuzzier is when you consider Goose Island. Started as a craft brewery, expanded and then eventually purchased by AB/InBev. They're still producing one of the best bourbon barrel stouts (Bourbon County) with continued expansion of the product and new variants (Cherry Rye) that are also quite delicious. So you wouldn't consider this to be produced by a craft brewery, but would you classify this as a craft beer? Keep in mind that they use (fairly) traditional ingredients and innovative recipes to produce a high-quality delicious product. It frequently does better in blind taste tests than other craft beers. While I don't like people classifying Pyramid/Red Hook/Widmer/Shocktop as craft beers, I think you could make an exception for Bourbon County (as well as their Belgian line up).