Instructions
Facebook
Launch a Web browser and go to the Facebook website.
Log in to your Facebook account with your email address and password, then click "Account" in the upper right corner of the page.
Select "Privacy Preferences" from the drop-down list, then click "Edit Your Settings" under "Apps and Websites" at the bottom left corner of the page.
Click the "Edit Settings" button in the "Apps you Use" section, then click the "X" button to the right of Mafia Wars.
Click the "Remove" button on the pop-up window to confirm that you want to close your Mafia Wars account.
Yahoo!
Sign in to your Yahoo! account, then click "My Yahoo!" at the upper left corner of the page.
Click the "Games" tab, then scroll through your list of games to find Mafia Wars.
Click "Options" on the Mafia Wars application box, then select "Remove" from the drop-down list.
Click the "Also Remove my Other Instances of this App from Yahoo!" check box on the pop-up window, then click the "Remove" button to confirm that you want to remove Mafia Wars. The application is automatically removed.
Chrome
Launch Google Chrome, then click the "+" button at the top of the window. A new page opens in a tab.
Right-click on "Mafia Wars," then select "Uninstall" from the pop-up menu.
Click "Uninstall" to confirm that you want to uninstall Mafia Wars.