This is crazy, I see double bookings on guests all the time when I'm pulling ADR's for people. The only thing that will cancel your ADR is you calling to do so. I'm not saying the CM didn't tell you that, I'm just realizing not all CM's are completely up to speed. WOW!
Also all this talk of people being asked for a credit card for locations that don't need them is strange because the screen we work on will only let you enter a CC # when it is an ADR that requires one. For example if I'm booking CP I couldn't hit the billing info button even if I wanted to.