Link: Michael Roebuck's Blog.
Integrating PayPal into your Yahoo! Store
If you are a Yahoo! Store owner and are using the new Yahoo Checkout, then you must be accepting payments from PayPal.
Before Yahoo! integrated PayPal with the checkout process, we were using a PayPal hack that inserted a PayPal link on the order thank you page. This was nice because it allowed customers to pay via PayPal and still comply with Yahoo! Terms of Service.
Mike is right! Start taking Paypal. The more ways you have for folks to pay, the more likely they are to give you money!