You can block up to 1000 users from your ebay auction
1:Log into eBay and go to your “My eBay” page.
2:Go your “My Account” page.
3:Click “Preferences”.
4:Under “Selling Preferences”, click “Buyers Requirement”.
5:Click “Edit”.
6:Click on “Buyer Requirements Exemption List”.
7:Scroll down and click on “Add an eBay member to my Blocked Bidder/Buyer List”.
8:Type in the eBay User ID of the bidder you wish to block from your auctions and click the “Submit” button. Make sure you type in the exact user id.
9:To remove a bidder/buyer from your blocked list, just delete the User ID in the text box and click the “Submit” button.