So I'm approaching this "kid" (late teens or early twenties) who's riding an MTB on the right half of the trail. I moved to the left side of the trail and dinged my bell because I was about to pass him. He turns his head left and looks right at me. Then turns his head back and proceeds to drift left. I said "On Your Left!" at which point he comes all the way over into my front wheel. (Yes, we've discussed the pitfalls of "on your left" before - I'd just never seen someone stupid enough to move left...)

At this point I'm on the brakes hard but he still got the wheel enough that I fell down and went boom at almost zero speed.

He turned around and apologized and I tore him a new one about keeping right, yadda yadda.

Long & short: Front wheel slightly out of true. Bike otherwise unscathed. I've got a couple of minor scrapes and a bit of a stiff shoulder. Nothing significant.

I suppose crashes are worthless unless you learn something from them. I learned that I have to announce a pass and let the other person get situated before actually passing. Though why he figured it would be smart to move left, after looking right at me, I'll never know.

Hopefully he learned to keep right.

At any rate I'm going to be a lot more verbal with people from now on...