I used the PB line in Brisbane today as the general line was as long as the terminal. No one in the PB line (or extra staff to scan the pass) so I let an elderly couple from the general boarding lane go first anyway before the agent called me forward, getting me and my colleagues BP's scanned - at which point the old lady I let go in front told me off for pushing in on the line.. The sign is pretty big, but it does feel odd having to push in at the front. I don't want PB to go away, but perhaps some friendly enforcement / education wouldn't go astray.