You're paying to check your belongings, so why should other people's excess baggage get a free ride? That's the question being asked by a growing number of travelers. As airlines look for new ways to boost revenue, fees for checked bags are on the rise; so is scrutiny of overweight customers whose baggage is built in. It's a touchy subject, Airfarewatchdog.com has found, and one that airlines have been happy to avoid discussing, where possible. As late as 2008, United Airlines wouldn't even address the matter with us. But an outcry among passengers, tired of their seatmates taking up more...