In a recent article in the Kosher Spirit Magazine put out by the OK Kosher, they answer this questions. I agree with them completely as the beer industry continues to expand and brewmaster in the US are always trying to find the new latest and greatest brewing craze in addition to the traditional beers. You really need to be on guard when it comes to beers and kashrus, the old adage of all beer is fine (in the US) is not necessarily true anymore.
http://www.kosherspirit.com/Article.asp?Issue=35&Article=516
