[Paul M]

I'm pretty sure you could reduce the active part to just one query ;

PHP Code:

$days = 1;
$points = 10;

$cutoff = TIMENOW - (86400 * $days);

$vbulletin->db->query_write("
    UPDATE ".TABLE_PREFIX."user
    SET reputation = reputation - $points 
    WHERE lastactivity < $cutoff 
"); 


You do realise that if someone doesn't ever login again - then their reputation is just going to get more and more negative each day.