There was a thread on FR a few weeks ago about British mailmen refusing to deliver election materials for right-wing parties that they don't like. Amazingly, their contracts allow them to refuse to deliver any mail they "disagree with."
The materials did get delivered, by management, because UK law requires that somebody deliver legitimate mail, but you ought to think twice about what sort of country we'd live in if USPS employees could pick and choose what they want you to read.
I just deal with ACT solitication letters the old-fashioned way: Rip my name off the pages, stuff just enough paper back in the Business Reply Mail envelope to make it weigh around two ounces, and send it on its way. I figure between the cost of printing, mailing both ways, then paying someone to open and toss the contribution-free envelope, it probably costs ACT about $1 all told to deal with it. And that's one less dollar they can use to attempt to destroy this country.
Even better, I'm on my seventh ACT letter so far. They must be using the same mailing lists over and over, because I only subscribe to a single liberal publication (it was free). And I do the same thing to John Kerry letters.
Cool ... What an innovative FReep!