I have the same philosophy as Spike. Over time, I've probably saved $10,000 on not getting extended warranties that probably would have covered, maybe, $1,000 worth of repairs.
However, I can see two situations where an extended warranty might be justified:
o For those that don't have or can't maintain sufficient emergency funds to cover an unexpected large repair.
o If you can't resist purchasing a vehicle that has a very bad reliability/repair history (although I've found that the extended warranty on such vehicles is very, very expensive - makes sense, huh).