There was a lengthy and generally thoughtful discussion of the ins and outs of mountain bikes in wilderness on the excellent website run by a local (to me) non-profit, Trail Keepers of Oregon:

http://www.oregonhikers.org/forum/viewtopic.php?t=21655

Of course, no forum discussion that runs 150 posts will be thoughtful for more than a few posts in a row. In case people wonder, the "Aimless" you see participating there is me.