Crossing lanes

I've noticed this, and seemingly more often the last few years. I don't have a car, so my experiences come from the back of a motorcycle.

When I see a "lazy driver" coming towards me with wheels on my side of the line, I give them an obvious "waving" motion, indicating that they should get back on to their side of the road. Not that it does any good, but at least I've let my feelings on the subject be known!