Hybrids are dirty.
You could do more for the environment if you were to purchase $3,000 worth of trees and have them planted in the rain forest.

Really.
Sure, hybrid cars run clean - based on existing vehicle pollution metrics. But chances are that whirring electric motors and nickel-hydride batteries also emit pollution, and there's no telling what the environmental cost will be 20 years down the line. There is also a question of recycling hybrid batteries. Right now, it really isn't an issue, because there just aren't that many batteries to dispose of, but that will change - and quick. This day will come, and here's the headline: Automakers Scramble to Dump Nickel Hydride.