I believe in most situations extended warranties are just a gimick. A way to squeeze 10% or 20% more profit out of the customer. But in the case of laptops it can turn out to be a major disaster not to have a warranty that protects your system beyond the first 90 days. If you have bought a lower end laptop (anything under $1000), then I wouldsay forget the extended warranty. The cost of adding another couple of years to the system could be an additional 30% of the purchase price. But if you bought a more expensive piece of hardware, depending on the system design, you could get more than your money's worth out of it.
We (my family) have owned nine laptops spanning the industry's vendors. IBM, Gateway, Dell, HP, and Sony. The IBM and Sony systems were the early units and we never had problems with them. We had an extended warranty on one of the Sony's and never used it, but it did become an attractive feature when I sold the unit on eBay. The Dell and HP systems were the next group of systems we owned and while I would say they were good units, I say this because we had extended warranties on all of them and needed them.
I don't believe in buying anything at full retail or even close to it, which is why I love Woot.com. I buy refurbished units. To my way of thinking, I am buying a unit someone else found the bugs in and so there is that much less chance of it failing, but it also means the system may be a year or two old, off-lease, lemon-return, etc. In most cases, refurbished laptops come with only a 90 day warranty. My experience has been that if you are going to have problems with a refurbished unit, they will not be the breakin type problems that electronics usually have in the first 90 days or so of operation. The Dell and HP systems we owned (refurbs) had major failures at the hardware level. Cracked motherboards, and fried cpu's. The problem with laptops can be how they are used. We tend to move the systems around a lot. Movement, carrying the laptop, depending on how they are carried can cause flexing of the motherboard and g-forces being applied to the entire system. Minor failures, such as fans not working properly caused one system to fry the CPU. The lighter laptops have less rigid case designs and seem to me to be greater candidates for MB flex problems. Our experience suggested that if you move the laptop around a lot, buy the extended warranty.
One other point, the laptop industry is a really neurotic market. Nothing stays the same for long. Models change almost every year in some cases. Some new models may just be bad designs or contain poorly spec'd components. We owned two, purchased new units (I violated my own standards, but the units were so cheap new, I couldn't pass them up, and they came new with 3 year warranties!), they each went in for repair a few times. They were the most problematic laptops we owned. There is no period for laptops where a model that has design flaws can be worked out in year two, three or four. If it is a bowser, it remains a bowser until they change models next year. So how can you know?
Some vendors charge an arm and a leg for the extended warranty. Since I buy cheap in the first place, I am not likely to spend $400 on an extended warranty. I will spend $100 to extend the warranty of a refurbished laptop out for a full year.