When a user is hidden from the Who's Online -- What about counting them in the anonymous list and not the registered user list?
IMHO --- It looks a bit weird to show 4 registered users in the top section but then just list 2.
If a person is hidden maybe they should be completely hidden from the who's online as a registered user.
Perhaps another option is to list the number of hidden registered users in the table.
IE.... 2 Hidden Users
Since a person could now figure out the number its not like its a secret.
