Wichita State University Software Usability Research Lab published an excellent article about the Top Ten Mistakes of Shopping Cart Design
The article is based on a survey of 500 top E-Commerce website.
Here are the top mistakes that we chose:
1. Calling a Shopping Cart anything but a Shopping Cart.
2. Requiring a user to REGISTER before adding an item to the cart.
3. Requiring a user to enter shipping, billing, and all personal information before knowing the final costs including shipping and tax.
This article is pure gold.