I recently spotted this gem on youtube, from Milltown Cycles, showing a dude riding UP a substantial flight of stair on what appears to be a custom-built mountain bike which uses 36 inch wheels.
Awesome! Check out the video below:
A number of custom frame builders are now able to build 36er MTBs, which use rims originally designed for off-road unicycles. The ideal application of such large wheeled MTBs should (in theory) lie in non-singletracky marathon events, but there is essentially no information published on the web concerning how much faster or slower 36ers can be compared to 26ers, 650b, or 29ers.
But watch this space!