Its more frustrating after standing in the queue for half an hour! I have seen it a few times recently at the LH economy checkin desks in Frankfurt. A single long queue through the baggage security screening and back across the departure hall. If you don`t listen carefully (German language helps) or even push your way to the front its easy to believe that since you are in the queue you will be checked in even if you are a few minutes late. I witnessed a great episode recently when an Italian guy in front of me made this mistake. He was standing at least 30 minutes in the queue and got to the desk about 5 mins late for his checkin time. The resulting arguement was a joy to watch with full gesticulation! (And he still didn`t get on!)
(Sorry, shouldn`t smile!)