I do it for the warranty and the amazing return ability they have. I had a camera break 3 years after purchase, manuf warranty was 1 year, amazon refunded the original buy amount...that's just one example.
Ohh, a recent one, I bought a $1650 laptop (Gigabyte p35x-v6) and it disappeared with UPS, so they resent me one next day air...few weeks later the other one showed up. I asked if they wanted it back, they said don't worry about it, its yours, haha.
I also had a friend order a TV stand for $350 or so, but they ended up giving him a Samsung TV that was $1500 or so, they also said keep that, and sent the stand free, hahaha. With the lack of stealing (B&M), they must have a lot of extra cash for accidents like this.
I am in the, I buy EVERYTHING at amazon, except groceries boat.