Dear Online Retailers,
Please do not force me to create an account on your site for what is most likely a one time purchase. I understand that you want my email to spam me, but there is no need for you to keep an account and probably store my password and credit card information indefinitely.
Chances are, if I do happen to shop at your site again, I won't remember that I have an account, nor the password for that account, and it will simply make it harder for me to check out with my potential future purchase. That is all.