My cable did disintegrate right before my eyes. I had the laptop about ten months when it failed. It looked fine, I plugged it in, I felt the plastic sheath crack beneath my fingers, looked down, and there were these beautiful wires!
I don't put stress on my cable, in fact my MBA is usually plugged in in the same spot, without tension on the cord or in a way that requires the cable to bend. I rarely bring the power adapter with me, as the MBA has more than enough battery life to get me through a normal day, so it didn't spend much time wrapped up in my bag. It frayed about 1 inch below the Magsafe connector.
I love Apple products, but when I look at the thickness of my MBA cable compared to all of the other adapters I have, it is significantly thinner than any of them. None of my other ones have frayed, and because their battery life sucks, those cables spent alot of time being packed and unpacked into a bag. That kind of thinness comes with a cost, in this case an increased risk of fraying. It is why extension cords are so thick. Decreasing size means increasing risks. I for one would prefer my power supply weighed a few grams more and took up a few more cubic centimeters but greatly decreased the risk that my power supply is going to fray, spark, and burn me or my house.
And remember, using something isn't abusing something. I don't think it is unreasonable to expect a laptop power supply to withstand years of being wrapped up and thrown into a bag, since this is exactly what they are meant to do.