Extended warranties are almost always a good thing with mechanical, electrical, etc items. The key to them being a good thing is the price you pay for them
Yea this is the only one that I can think of that I have bought...It's just a bet - the odds the unit will fail in the warranty period vs the ratio of premium cost to replacement cost. You can be sure it's a poor bet for you and a good one for the warrantor.
However, a sense of peace of mind often influences people to get them anyway.