I fly with carry-on but discovered that packing light now has a new meaning for international travel.. On my recent AirFrance flights to and from Paris I was limited to 12k in weight for both carryon and personal item. My bags are small, easily fitting in the overhead and beneath the seat, so of course I questioned the agent, who  directed me to a nearby scale. Sure enough my two bags totaled 28 pounds, more than the 26.4 pounds that equals 12 k. So one bag had to be checked.

I was relieved to be able to check it all the way through to Montpellier. If I'd had to claim it and recheck it, as international passengers must do upon arrival in the U.S., I almost surely would have missed my connecting flight. But Passport Control in France is much simpler than this country's customs and immigration, so it turned out to be no big deal. After a brisk walk between Charles de Gaulle airport's Terminal 2F and 2E I arrived in time for my flight to Montpellier and found my bag in good shape on the baggage carousel when I arrived.

I also  had encountered that weight rule on my return flight from New Zealand last fall so I guessed, correctly, that it's a rule that's now something most airlines observe. Air New Zealand has a 7k limit (15.4 pounds)
An online search reveals that these limits are mostly for economy class flyers. Fly first or business class and you can carry on more weight.  Check it out yourself at http://tinyurl.com/d997rpk