Do mountain bikers yield to hikers?
The usual trail etiquette rules are, basically:


Cyclists yield to everybody
Everybody yields to horses
If you're both cyclists (or both hikers, etc), somebody going downhill yields to somebody going uphill


So as a pedestrian going uphill on a narrow path, the cyclists were supposed to yield to you.  However, if you looked like you were stepping off the trail, they probably assumed you wanted to let them pass.

Yield means something like: slow down to the hiker's speed, and if needed pull to the side and let the hiker pass, and depending on conditions would likely mean needing to stop entirely.

See also:


http://www.imba.com/about/rules-trail
http://www.imba.org.uk/WhereToRide/TrailEssentials.html (the UK says "Give Way" instead of "Yield")
http://www.romp.org/modules.php?op=modload&amp;name=Sections&amp;file=index&amp;req=viewarticle&amp;artid=8#hikers


Cyclists that don't yield on trails scare other trail users and eventually lead to controversy over cyclists on the trails and possibly closing or limiting access for cyclists to those trails. For instance, Mount Tamalpais was important to the original development of mountain biking, but cyclists are now banned from many of its trails.