Overcomplicating the checkout process
Checkout processes are supposed to be made as easy as possible for customers to complete. Of course, a certain amount of detail is required to complete a transaction, but this should be made relatively painless for the user.
The checkout and purchase process should be smooth and easy to understand, distractions should be removed, while the amount of information required and the number of steps should be kept to a minimum to make it as quick as possible. This is not the case on VistaPrint though, which has one of the most complicated checkouts I have seen.
