Have been removing bumper stickers gradually for some time. Why give the traffic/revenue cameras more evidence.
Last summer I drove around down with a Ron Paul bumper sticker on my car... driving no different than I usually do, I got three speeding tickets within a month.
Yes, I was speeding... but no worse than I'd been before the bumper sticker went on. I paid my fines, peeled off the sticker and started watching my speed more carefully, and haven't had a ticket since.