I just came across an article titled Doubts Cast on Hybrid Efficiency (HT: Signal vs. Noise) that essentially says that Hybrids are less efficient than their conventional counterparts. Interesting.

A research study was performed that calculated the total energy cost it would take to plan, build, sell, drive and dispose of a vehicle from initial concept to scrappage. When we only consider the fuel efficiency of a car, we miss out on a lot of stuff. And it turns out that far more energy goes into building a hybrid vehicle than into a conventional vehicle.
For example, the Honda Accord Hybrid has an Energy Cost per Mile of $3.29 while the conventional Honda Accord is $2.18. Put simply, over the "Dust to Dust" lifetime of the Accord Hybrid, it will require about 50 percent more energy than the non-hybrid version, CNW claims.
And here's a shocker:
while the industry average of all vehicles sold in the U.S. in 2005 was $2.28 cents per mile, the Hummer H3 (among most SUVs) was only $1.949 cents per mile. That figure is also lower than all currently offered hybrids and Honda Civics at $2.42 per mile.
The conclusion is that things are always more complicated than what we're led to believe:
Basing purchase decisions solely on fuel economy or vehicle size does not get to the heart of the energy usage issue.