I purchase items online all the time, but I've never bought anything from Amazon. In my opinion, they collect too much information about their customers and use it in unethical ways. This CNet article notes even more intrusive data collection by the online giant.
Amazon is going to start using information on client purchases to recommend gifts, and tries to guess age, gender, and their birthdate. The article notes that this may violate child privacy protection laws in cases where Amazon is trying to guess that information for your children.
One of the things I don't like about Amazon is that the company is relentless in trying to get you to buy more stuff, masked in the guise of being "helpful." It's as if we aren't able to make up our own minds about what we might want or need--we now need giant marketing databases to help us make decisions.
I still maintain that my local independent bookstore is a better deal than Amazon. I can call them on the phone and place an order for a book, start to finish, in under a minute; they usually give 20% off special orders; they don't charge shipping; and the book usually arrives in 3-4 days. And I'm supporting jobs in my local community.