Theoretically, a small pickup can be made fuel-efficient, especially at low speeds where aerodynamics don't matter much, but then it would likely fail at being a good pickup. Most people who drive pickups need to carry or tow alot of weight, which no current hybrid is good at doing... I think there's one SUV hybrid, I forget which, that can tow 1000 lbs. It's probably the 26 mpg Highlander.