Well, this guy seemed content to stay on the right half of the trail until my front wheel was next to his rear wheel. Then he darted over pretty fast.

I do have a theory that he tried to play Lance and keep me from passing him (we were going up a hill). That would explain the sudden change of direction... He pushed on the bars trying to power-up.

At any rate, my wheel is now straight and they replaced my worn bearings in the front hub so it was sort of worth a visit to the LBS anyway.