Create block user flag, hide users from view
I couldn't find a way to do this within Views, despite the seemingly simple task and the various decent explanations found around the internet (nit3ch's comment included). The explanations limited the view results too much or in the wrong way. 

I ended up using a Views PHP filter field to perform the filtering task:

global $user;
$flags = flag_get_user_flags('user', NULL, $row-&gt;uid);
if( array_key_exists('block', $flags) &amp;&amp; array_key_exists($user-&gt;uid, $flags['block'])){
    //dsm($row); // optional debug
    return TRUE; // prevents row from being displayed
}