I commute to work by light rail. I have a folding bike and all, but it's 0.8 miles to the North Avenue Light Rail and 0.7 miles to the Cultural Center Light Rail. When I get off the rail, I can orient myself by glancing around and spotting the building I work in. The light rail shuttle (light rail is down right now in that area) is about 4 feet from the parking lot; the light rail station is about 150 feet away.

Problem is pulling the bike from the garage and getting changed at work seems to be a wash versus just walking it to the station. On the other hand, the bike goes FAST; maintaining 15mph on a bike is a leisurely walk, and any form of running (6mph, 8mph...) would be better spent beating Lance at a track run. Seriously, if I wanted to expend that much energy, I'd race cars on my bike.

How short does your commute get before you start just walking it? Is there a distance where it's too annoyingly long to walk, but too short to bike without wasting a bunch of time gearing up?

At least I've put a bunch of miles on the Vibram FiveFingers I got.