Weight limits
As far as I was aware most airports operate the same way, an airline stipulates a carry on luggage size/ weight & number limitation. This is first checked at check-in by their own agents or airport check-in staff. As you pass through security most have size gauges to regulate what passes beyond that point, (weighing at this point is an optional extra).
However it is not unknown for certain passengers who fly regularly to try and avoid costs by purposely hiding luggage from check-in staff and after receiving their boarding card will then try to take the extra baggage through security. This is where the differences often occur, each airport has it's own interpretation as to how they deal with such passengers, some turn a blind eye and say it's not a security function it's up to the handling agents to stop and deal with at check-in and other airports make security rigorously send them back to check-in so that airlines do not dip out with the extra charges incurred. It just depends on where you fly from as to how you get treated, as for obnoxious staff their probably just being as obnoxious as some of the pax trying to cheat the system!!