When someone speeding slightly over the limit passes me safely I do nothing, even if I was going near or over the speed limit. But if they pass me unsafely, or at an extremely high rate of speed, then that IS my business and I will let them know. Usually I will issue the "slow down" signal. Hand flat with palm facing down, pumping up and down as if to be pushing towards the ground. This is the same signal speeders get when they race though my residential area while I'm in my front yard or driveway. It's nowhere near as good as an officer giving them a ticket, but it doesn't hurt to let them know that someone is watching.

If I get the chance I will talk with them, but since my routes have long distances between intersections this rarely happens. Doing this causes me no extra stress. As a matter of fact, I would be way more stressed if I didn't do or say anything in response to something that could endanger my wellbeing.