Disable customer in Magento

This is an interesting one. I've looked into this previously, and there is an is_active flag on the customer database record, but it is not accessed or written anywhere by the core Magento code. In order to achieve this requirement, you'll need to override the Mage_Customer_AccountController to check the value of this field inside loginPostAction() and then to make that field visible within the adminhtml Customer blocks.

I'm a little nervous about implementing that code as it bothers me that Varien would include the field but not utilise it at all. I'd be interested in others' thoughts about this.

HTH, JD

Or, you could use this free extension from Magento Connect.

magentocommerce (deadlink) Customer Activation Extension

edit: Github project