Amazon’s single sign-in, one-click ordering and variety of goods provide a lot of conveniences. However, it’s quite easy to manage e-commerce information and purchases on a variety of websites. I recommend use of a password manager.
My favorite is AgileBits’ 1Password. It securely stores my personal and business information and shipping addresses, my credit cards as well as many website logins. It works on my phone as well as my laptop and desktop computers, fully synchronized. It’s browser plugins allow me to login to many stores with a single click, provide my shipping information and credit card data with a couple more.
I highly recommend these kinds of products for web logins and shopping, as referred by Lifehacker’s Five Best Password Managers:
There are also privacy benefits from spreading your transactions amongst multiple websites, as opposed to having Amazon know everything you’ve ever browsed, clicked and purchased.