The last few times I have flown, the airline (Delta) stated specifically that we were each allowed one carry-on that would fit under seat, or in the overhead bin, and one personal item, like a handbag or a laptop case.
Do people violate this? Absolutely, but, keep in mind, the airline has the legal right to make you check any bags that exceed this limit. I had this happen in Hong Kong, and, maybe, they are more strict over there, but I certainly wouldn't want to bet the farm on it.
Plus, EVERYONE has carry-ons, and you may be taking up a space that someone else could use. I know if I had to check my carry-on because someone had 3 bags, and a luggage cart, I'd be royally ticked off.
I'd re-think this if I were you