Hah, I'm not really that knowledgeable about it. I have the same thoughts about zones as you. I know that the authorities out there advocating zone training say that you need to do your 60% recovery rides at 120bpm or whatever even if you are barely staying upright on the bike, but I don't think so.

Even so, your zones will start below 150. Zone 1 is your "slow walk" zone basically. In fact, at least your first 2 zones will be below that.

It's not totally useless. Seeing how my body likes to work explains why I am not an ultra-endurance cyclist. I'm not even much of a regular endurance cyclist. When I ran, my events were 100 meters long usually. That means I'm efficient at working at high heart rates, but I cannot really do much at the low ranges. So maybe that's why my legs want to explode after doing even a metric century.

Anyway, here's a good article:
http://www.cptips.com/hrmntr.htm