Please read this splendid little interview with David Simon, creator of HBO's The Wire, which I've never actually seen. Think I'd like to, though -- maybe when and if it comes to DVD.
And notice the setup, in which the interviewer describes the thrust of the series' second season when "the program explored corruption on the waterfront, with the tale of a union official who dealt with criminals not to feather his own nest but to reverse the declining fortunes of the port, with terrible results; the story was closer in spirit to a classical tragedy than a police procedural".
Sound familiar? Maybe if you read all the way through this post in which I discussed (my take on) Kazan's motivation in On the Waterfront. Best intentions laid bare, and all that. My hunch is that Simon feels this way about most institutional efforts - that rot will creep in.
I'm pretty certain this is his diagnosis when it comes to the drug war.