Yeah, tapping the taillights is actually useful for indicating that you may need to slow down due to conditions ahead and that someone behind you needs to beware. What pisses me off with motorcycle riders is when they get those pulsating high-beams. I basically have to adjust my mirror so I can't see them and can't help drive carefully around them.As I understand it, flashing the taillights (lightly tapping the brakes so that your brake lights light up but no significant braking occurs) is different from brake checking (hard braking).