So I read IMBA's article on it here:
http://www.imba.com/resources/bike_management/trail_diplomacy.html
Its a nice article on sharing the trail and such, but I'm still a bit confused. Between us bikers, who has right of way, uphillers or downhillers? I've been given the ROW when going up and down. I've always tried to give the ROW to uphillers, but some move out of my way saying to let'er rip. I've also been almost run over by some downhillers with no regard.