If you purchased something from a merchant using Yahoo! Wallet, you will be billed--the purchase isn't canceled.
Any Yahoo! premium or subscription services (such as Extra Mail Storage, Featured Auctions, GeoCities Plus, or Website Services) set up with your Wallet will be cancelled, and any outstanding balances will be charged.
You will still have a Yahoo! Security Key, which you can use for other Yahoo! services. If you want to use Yahoo! Wallet again, you will need to re-enter your credit card information. Your home or work addresses will still be stored at Yahoo!--you can edit or remove them by visiting Yahoo! Account Information.