登录MobileMe
在控制面板里能注销帐号

http://support.apple.com/kb/ht2174

If it's been 45 days or less since you were charged on your credit card for a one-year MobileMe subscription, or you are currently in a free 60-day trial

Follow these steps to cancel your MobileMe subscription:

    Go to the me.com/account and log in.
    Click Account Options in the sidebar (on the left).
    Click Cancel Account at the bottom of the window.

Your account will be deleted after you confirm the cancellation.

Note: If you've removed the credit card information from your account, the Cancel Account button will not be shown. Replace the credit card information for your membership in Billing info to see the Cancel Account button.