I've never had a problem with cyclists on mountain trails, probably because there don't seem to be very many of them above a few hundred meters elevation gain, and any who are riding there seem to be mostly polite and friendly.
However, Edmonton has some beautiful river valley trails that are posted as 'Shared'. Some are paved but many are gravel or dirt. There, people on mountain bikes almost universally seem to have a 'get off my trail' attitude. Just going for a walk on a summer evening means risking a collision with some idiot flying down a busy path at full speed. I'm fairly nimble - I can usually hear them sneaking up from behind and jump out of the way - but I pity someone who's disabled, hard of hearing, or just not paying close attention to their surroundings.
Local bylaws say that cyclists [u]must</u> ring their bell when passing pedestrians, but it's hard to enforce. On one evening's walk, I was passed by at least 100 cyclists. One rang a bell as he approached from behind, and two or three called out to let me know they were coming. The rest seemed to be more interested in seeing how close they could come for maximum 'startle value', and many snarled and/or glared at me as they passed, for the sin of being in their way. And almost none actually seemed to have a bell at all.
Hopefully none of the people on CT are like that. Those attitudes make one want to walk firmly down the middle of the path so the cyclists can either run into a well-padded backpack or off into the bushes. Obviously, the bad ones stick in your mind more than the ones who are polite, but it's a case of those few ruining it for everyone else.