OK I know in the past it was a b*tch to remove your credit card which required a call to Microsoft XBL support. And even that was a pain to get it removed.
Recently Microsoft merged GFWL and XBL into one. My guess is because Windows 8 will get XBL support. So now to remove your credit card from XBL is just as easy as it is on PSN.
You sign in to your XBL account on http://www.xbox.com/en-US/ Now got to My Account --> Payment and Billing --> Manage Payment Options -->
You'll now see a list of all your credit cards listed with your account. On the right hand side of the page you see the Remove button. And there you go. This is helpful if you have one of those kick @ss deals that Microsoft promos but is subject to recurring billing. Although i'm not sure if they will block you from removing your only payment option.
It's also good if you don't trust either Sony or Microsoft with your credit or debit card info.
P.S. Microsoft now accepts PayPal as a payment option you can set as a default on your Payment Options.