Posting in the Magento forums has been disabled pending the implementation of a new and improved forum solution which should better serve the community.
For new questions please post at magento.stackexchange.com, the community-run support site for the Magento community. We will be providing updates on the new forum solution soon. For questions or concerns please email email@example.com.
Blocking a particular customer to keep away them from your shopping list can be done by blocking their IP address, if it’s existing customer you can identify their IP through previous history details in your shopping customer details. However, if you don’t know their IP you can’t block them until you know their IP.