Biggest problem I have is the Political stickers on the back glass, but only close to election time. The GasSavers.org sticker requires a driver to be right on the bumper to see it (angled hatchback), so they figure it out and go around or follow on the highway out of curiousity.
People have to be ready to save fuel -- no way to force it. Advertising and have people visit this site when they're ready is the best way to go. I slip it in now and then in casual convo as well. We're fortunate right now that we're in a Green renaissance -- but -- (Trying to be as politically unbiased as possible), it's tough in the State in which I live to be "Green". Other states are tougher (especially in Oil-rich areas), I will admit.