As far as I'm concerned - it's totally fair. A recent flight back from BKK had my carry-on weighed and it was found to be over the limit. Had to remove some stuff into a plastic bag (some treats bought in the terminal for my co-workers). Plain and simple, it is a safety issue and I applaud QR for taking this seriously. Many airlines (BA) allow people to take ridiculously large carry-on bags and boy, do I complain about that.