I read once that hybrid cars are actually a lot worse for the environment than their regular counterparts because of all the advanced manufacturing processes that go into making hybrid vehicle batteries. Unfortunately I didn't retain a link to the article but it basically pointed out that between the mining to get the materials, processing the materials and shipping them to the appropriate places the manufacturing process created more green house gasses than any car could ever dream of producing in it's lifetime.
Not sure on the validity of this but it certainly is thought inspiring.