I'm trying to restrict a promo to only certain people in a shoot, specifically to people who have placed an order but had trouble so I can send them a make-right promo. Right now, I can only change their status individually to get it done, and there could be a good reason I have a client set to something specific, don't want it changed. Since I can layer on Client Groups without affecting anything, they're the better choice for targeting. A filter obviously opens up all kinds of targeting over just client groups (while including client groups).