Caroline, I was shocked at how much force was in that bag as it plummeted into the row in front of me (even though it was still light enough for me to hoist over my head--I don't know why my grip slipped for a second). Though no one was in the row, other people were in the cabin and I got The Stare from several pax and FAs (deservedly so). I was hugely embarrassed, but even more hugely relieved I hadn't hurt anyone.
To this day, I shudder at the thought that a baby could have been in one of those seats.
So even though BA's never bothered about carryon on my flights with them, I do NOT suggest (and never did!) that it's ok for people to drag along heavy carryon items. I don't care if the airline says it's ok to bring the kitchen sink on board, my carryon is as light as possible.

althom1122, you can put the toothbrush in your checked luggage. Even in economy, you get a little kit with a toothbrush in it (not a good one, but it's ok for a flight).

I think cultural differences are at work here. What's the carry-on policy with other European airlines? In my experience Americans carry much more stuff about than we do. Something to do with travelling further and longer so needing more stuff? I always travel BA (3/4 times a year) and have never had a problem with luggage, checked or carried. And at the other end (LGW in my case) the bags are always off the plane before I'm through immigration, so what's the hurry?