You don't want flex in the wheel, but it can be stiff with thin spokes.
You can build as light as you are willing to assume maintenance.
Make it fool-proof, and I will make a better fool.
Norco A-Line, 50+ Mph dirt bike and winter commuter... sold
Specialized Demo 8 performance dirt bikehttp://img715.imageshack.us/img715/5824/dsc03417ae.jpg
Santa Cruz Heckler, lightweight road racer
Santacruz V-10, performance dirt bike
Work in progress:
Trek Session 10