Having worked for a bit in the Used Car bizness, I know first hand they are a rip off.
As Torque states, there is always a catch they can get you on. Some came w/ a deductable even after you spent the $700 for the warranty. Keep a repair and maint. fund if you can. Dealer Extended Warranty only if you must.
Uhhh...if the universe is still expanding, WTF is it expanding into?