WhoKnows can help users build their profiles by automatically deriving skills from online work activity. WhoKnows protects each users' privacy by only analyzing work-related activity (via topic filters) and ensuring no derived skills are ever published without the user reviewing them first. In addition, the network admin can also further restrict work activity by URL/domain white lists and black lists. Here's how.
Go to the Admin link in the account dropdown.
Go to the Settings page and the Who Knows What tab.
In the "Don't analyze work on these sites", you can add specific domains or regular expressions of sites to block (e.g. *.facebook.com).
Then, you can add exceptions in the "Except for these sites" field in the same manner (either specific sites/pages or regular expressions).
Optionally, you can allow users to add their white list or black list entries if they want further control.