For starts anyone who posts on a commuter list a quote praising the pleasure of pain while cycling: ala "My legs are burning, my lungs are raw and I can feel my heart beating out of my chest. It's good to know your still alive eh"

For seconds anyone who is anal enough to log his daily commuting miles and post the figure as his signature.

Third and most important, a passion for finding some pretext for feeling superior in some manner to other cyclists.