Unions by their very nature lend themselves to corruption and the hijacking of the agenda by the select few for the benefit of the select few. Union organizational structure is severely lacking in the sorts of checks and balances that are prevelant in, say, a typical democratic form of government.
Unfortunately a union is a necessary evil in this profession, and it would work a WHOLE lot better if EVERYONE were part of the same one instead of ALPO, AAPA, SWAPA, Teamsters, etc. AA really boned us all on that one...