You can manage friends by selecting "Invite friends" from the menu and clicking on the "Manage" link. From this page, you can select which friends will be able to see results that you have saved when they do a search for related terms. Semanti is currently 'all in' or 'all out' and changes you make will not be based on timing, (You can't block someone, complete some searches and then unblock someone. They will be able to see all of your results).