Recapped tires are dangerous as hell...but they're on the back of almost every semi and trailer on the road. I've had pieces of retread thrown up by other cars and hit me in the chest while riding my motorcycle- small pieces, but they still thump really hard even through an armored jacket. I don't ride anywhere near semi trailers, but you don't have to be close to at highway speeds to get into the "dirty air" behind them. I've never actually gotten close enough to one to feel like I'm in the bubble drafting it.

As far as being rear-ended by some inattentive driver at a light or what have you, the rear-ender is getting the short end of that stick via a B&W ball mount.