Wow...I would have shit my pants. That guy is lucky that he was on a smooth trail. I typically ride trails rougher than that, so it wouldn't have been as easy to ride fast. And bears are deceptively fast....you can't outrun then, but you should be able to outpace them on a mountain bike.
The really surprising thing in the video is that the bear kept chasing for quite a distance. Bears are quick in short bursts, but they can't keep running quickly for long distances. And how strange is it that the guy was able to hide behind that small tree with the bear not having any idea where he was? Was that a gunshot that scared off the bear at the end?
Looks real to me, but most people think it's fake....