./wp-includes/user.php:251:function get_user_option( $option, $user = 0 )
./wp-includes/user.php:293:function update_user_option( $user_id, $option_name, $new_value )
./wp-includes/user.php:322:function delete_user_option( $user_id, $option_name )

Array
(
   [blogid1] => Array(1,2,4,7),
   [blogid2] => Array(3,6,8,10)
)