In my experience, the number of people that actually have what it takes to telecommute effectively is extremely small, and most of those are self-employed already.

Of those that want to telecommute and have a steady job, very few can actually handle the responsibility and the lack of stimulus from co-workers for longer periods of time. Flexible hours, working from home on a regular basis, sure, no problem, but actual full time telecommuting requires a lot of commitment, discipline and communication skills.