Before making a purchase, I usually browse Amazon, read the reviews, and make a decision. I then purchase locally. I'm long past trusting salespeople except maybe in regards to fly fishing.
The decision to buy locally is an ethical one meant to support the local economy. By the reasoning of some in this thread, perhaps I am unethically using Amazon. Yet I feel Amazon can shoulder the weight of having become a necessary source of information. Years ago I lived in Seattle and supported Amazon because it was a local company.
I suspect that many people have shopping habits similar to my own.