Flew to Brisbane last week with You-Might-Get-There airlines (Tiger) and they weighed all hand luggage going on board, causing a few casualties. On the way back we were sitting next to a Jetstar gate waiting for our flight and spent a very amusing 45 minutes watching them check all that flight's carry on. Several smug women would saunter up and put their bag on the scale (usually just on 7 kg) only to be told they also had to put their handbag on as well (usually another 7 kg), the smiles soon disappeared. Businessmen with carry on and laptop bag would usually come in at the 14 - 18 kg range. Lots then agreed to put bags in underneath at $50 a go. The two best were a early 20s shapely young girl trying to discreetly pull on a pair of jeans while still wearing her very short mini and tights, gave up in the end and went to the loo. The second girl had 18 kgs of luggage. Tried various ways to get the bags weight down so the hostie would put the ok label on them. She was even sprung piling up her clothes behind a wall so she get the label and then just refill the bag for the flight. In the end she boarded the flight wearing about 5 layers of clothing, looking bigger than the Michelin Man, she would have been almost impossible to sit beside and would have been very uncomfortable.
I suppose this long ramble is saying, depending on who you are flying with, be careful about the weight. Second point is that with the Brisbane Tiger flight (was actually early), there must have been only about 20 bags off the flight and we would have taken about 2 minutes longer to leave compared to us not taking any checked luggage ($15 a bag).