I've occasionally been marginally overweight, and the Agent has turned a Blind Eye, but recently checked in using an electronic ticket at an automatic check in facility, my slightly - less than 1 k - excess weight rang the bell, and all the automatic extra over charging systems came into play.
I played dumb and cancelled everything and asked for assistance, the standby agent, actually working harder at trying to sort out everyones' problems with the D.i.Y machines than if she had just been efficiently processing everybody, regretted that she could do nothing to override the slight overweight. The Computer Has Spoken, so I put some of the stuff from my hold baggage into my cabin bag, and The Computer was happy.
Now, the aeroplane took off with a false loadsheet - OK, not important in this instance, but you get the point ?
Life was easier before computers - as someone else has remarked, I Blame Bill Gates.