I've just gotten in a habit of looking over my shoulder on curves, climbs, before intersections, taking off from a light, wherever, and occasionally just to make sure no one is sneaking up. Which does not happen often but nice to know what is around you. And I think it should be your responsibility to know what if anything is behind you, who it is, what kind of rider they are, and maybe even where they are headed. Met a lot of nice people that way who are very grateful for the pull. Most latch on after you pass them or when you catch them at a stop light.

Being a clyde at 6'5" and one who gets many a compliment for the nice pull or work on the front you get used to riders who are strong enough to hang on, or try as long as they can, and they can enjoy the draft behind a mack truck. More often then not they say thanks, or they just fade away.

Once I know they are there by shadow, or noise, or announcing themselves I will acknowledge them by pointing out an obstacle. If they pass me and want to pull for a bit, I'm ok with that as long as they don't slow the pace down or get in the way with scary riding. If I end up doing most of the work - no problem. Enjoy the ride. Just wished there were more fast big guys for me to get a good draft behind.