I'll have a crack at this.
A "Beer GeeK" is a beer drinker, probably not a brewer, who obsesses about beer brands. A beer geek knows all the craft breweries, their personnel, their beer lineups, their stats, the seasonals. The beer geek endeavors to taste every beer that meets his threshold definition of "quality", and freely opines about that beer's characteristics, strengths and weaknesses. The beer geek isn't limited in any way to locally produced beers, as he's tied into a network of trading beer geeks, all, like him, seeking to expand their beering "life lists".
A "Beer Snob" is like any other snob, that is, if you don't rise to his or her level, you're not worthy of pretty much anything, including the beer snob's attention. A true beer snob, when met with the classic "I don't like dark beers like Guinness, they're so heavy and bitter", will smile a knowing smile, say something like "oh, yes, of course" and look over the ignoramus's shoulder for someone more suitable to talk to. After all, a snob is a snob, and why waste the effort?
A "Beer Dick" is one who just won't shut up, because someone, anyone in the world doesn't know much about beer and, of course, that person MUST be chastised, educated, refuted and cajoled until he admits that he doesn't know much about beer and that he "really should" learn.
