[support] Need a module for user blocking other user.

I am in need of a Drupal module which will enable all authenticated users to block other users. Like the feature in Facebook and Orkut.This feature is required for a social community networking website which all content (audio video photo document) uploads. Please help me with a module or a easier way to start a custom module with out extra load on MySQL query. Thanks in advance. Thanks & Regards Vasanth Govind