See Andy's other stuff:
Anything that slows down the purchase process is a bad thing.
Example: Does your web shopping cart ask what kind of credit card the customer is using? Your form can figure it out from the card number.
One less step = faster checkout = happier customer = more word of mouth and repeat visits.
Step 1: Find and remove anything between you and the customer’s money.
Step 2: Are your programmers thinking about less work for the customer or for themselves?
Learn to get people talking about your company, cause, or idea.
Learn more >>
We're the community for social media leaders at the world's greatest brands. Learn more >>
You can have amazing word of mouth, and I can help you do it.
My New York Times bestselling book, Word of Mouth Marketing: How Smart Companies Get People Talking, is full of practical, how-to tips on how you can get more people talking about you tomorrow. Book site | Amazon
My keynote speeches about word of mouth marketing and social media, will leave your group energized, educated, entertained, and enthusiastic about the power of word of mouth.
My companies:WordofMouth.org: 
Learn to be great at word of mouth marketing.
SocialMedia.org: We're the community for social media leaders at the world's greatest brands.
Contact me:Click here, I'd love to meet you.
Er, your shopping cart for your book asks for type of credit card. But I agree wholeheartedly with the idea. Some businesses make it soooo hard to buy from them. What is it with that?
Great point on usability–too few people think about minimizing friction!
When it comes to credit cards, though, I actually went through this exact debate a couple of weeks ago. My company opted to leave the choice in for usability’s sake: when we tested with users, it was much easier for them to think of “my card fits/doesn’t fit in these categories” as an option in the form, rather than a guideline (ex: “we accept Visa, MasterCard…”). People got confused when we couldn’t process their card because our merchant account won’t accept it, and offering that choice minimized errors with no effect on form submission.
There *are*, however, a ton of cases where we removed unnecessary options. I just hope our experience with this specific one can help some readers!