some say at 1600, I think never.
it just happens more rare the higher rated you get.
hanging pieces is most because you cannot see the whole board.
as you get full board awareness you are less likely to make errors as your focous is on the whole board not a specific area.
you are making an attack but forget backrank and so on.
It is rarer as your rating gets higher, but even grandmasters overlook mates in one and hung pieces and hanging their own. Case in point, I hung the exchange recently and a pawn in another game almost on the same day (2 different games).
Tip: Stop playing those fast games, blitz, etc. You're not likely to get over making dumb moves by playing fast. Play the ONLINE CHESS, where you get to take your time and SEE more things and check your board. THEN you're going to improve on not making dumb moves. Run your mouse over a person's name and you'll notice the rating they get AND you'll see what they mostly play. Yours is blitz games. Run your mouse over all the people who responded here and you'll see online games. Same thing happened to me and most of us on here. As you play more and more online, slow games, the dumb moves will start dropping off. Always ask yourself at least 2 things after your opponent moves: 1) Why did he move that and can he get any of my pieces? 2) After you know what move YOU will make, ask yourself, Can he get any of my pieces for free?
Most beginners only consider what THEIR next move will be, but as you get batter, you'll first consider WHY did he make HIS move?
Again, stop the blitz games and start playing online games and take your time.
i would say 1200
but it depends if you mean dumb being dropping pieces
Never, see my last game and the WC match.
At what rating do you see players stop regularly making "dumb" and obvious mistakes, such as hanging pieces, failing to defend against easily defensible checkmates, etc.?