I think Amazon needs a mass-media ad campaign. In particular, they should promote the more mundane items that they carry--packaged foods, health & beauty aids, stuff you normally might get at Wal-Mart. I buy a lot of this kind of stuff at Amazon. Not strictly for price, though it is usually very competitive. But also for convenience. Instead of having to put it on my Wal-Mart list, then hope I remember when I got there for my monthly shopping spree--I just put it in my car, now. It gets ordered as soon as I hit the low, low $25 threshold for Super Saver Shipping.
Another thing they can promote are the benefits of their reviews. Never buy a consumer durable without getting a virtual test-drive, courtesy of the reviews.