I cannot stand having someone with more than the item count posted going into the express line. I am the customer who will say something to that person, usually - "Excuse me, perhaps you missed the sign that this is an express lane for fewer than xx items?"
If the person says (rarely) "Sorry, I didn't see the sign - please go ahead", then all is well. MOST of the time they say something like they are in a "hurry", "don't feel like waiting" etc..
Then I break into baseball style chatter about how inconsiderate they are, selfish, egotistical...etc...etc..in my own little attempt to shame them or at least maybe have them think a bit harder before they pull it the next time.
I think the cashiers SHOULD redirect shoppers to the appropriate line. Most all of us would better appreciate that approach instead of just forcing those of us who follow the "rules" to be punished cause the store doesn't want to step up and do the right thing.
Target is the worst store in our area for check-out. Why they wasted money on 30 check-out lines when they typically only have 2 or 3 even open is beyond me. Target has lost it's luster for me.