With all respect, I disagree with most of the opinions posted. In my experience and in most consumer studies, extended warranties are not worth the cost. Your mileage, preferences, and needs may of course vary.
If an extended warranty costs 15% of the price of the product, it makes sense to calculate the odds of the product going south in Years 2 and 3. If something goes wrong in Year 1, it's covered under the normal warranty. If something goes wrong in Year 4, the extended warranty doesn't help.
I've owned 6 or 7 laptops in my lifetime and none have ever required repair. Extending that to electronics in general, in my experience, things generally are wonky out of the box or they're fine.
I understand that Apple Care is available at a cheaper rate from re-sellers. In this case, it might well be worth it but Apple's costs are on the high side. I don't use a lot of telephone support services but this alone may be worth it for some people. Also, those who re-sell their equipment may get more by being able to offer a warranty.