The way the data is set up there are some contacts that are only in civicrm and some that are in civicrm AND registered at the site. Registration status changes as people come to the site.
Currently, the only way to differentiate these two statuses is to use the uf_match table.
It would be very helpful to have this information exposed, both for the purposes of subsetting two groups of records that differ in important ways and, optionally, for the purposes of protecting the privacy of individuals who have not opted in to the site from profile listings that are available to site members.
also add an unselect to the radio box if the user does not care about this and wants to revert