I can see the concern. I can only say that for myself, anything high dollar or important....iPad, phone accessories, any important paperwork etc.....always is in a carry on that fits underneath the seat, normally along with a quick change of clothes in that one personal bag. The actual separate carry on suitcase I have always fits in an overhead bin, but in case it doesn't or there isn't room, that carry on will have nothing critically important in it that would/could be harmed by gate checking. Just a little preplanning which has served me well so far in terms of worrying about important items or not.
While I was typing this out and thinking of things I could lose I guess the easiest option that occurred to me was a small personal bag for anything valuable. Luckily I've never been out of overhead space and with the newer plane designs soon to be introduced or becoming more widely spread I wonder if it'll be something I ever have to worry about. I'm anxious to fly the MRJ and C-Series. I've flown on some of the newer 737s with the space bins and was very impressed.