I think the idea is that you can leave a cell phone plugged in; I know for a fact that it won't drain the battery. Now if you plug your 12v toaster into it you might have issues. IMO if you can afford a 30-40k car you are responsible enough to know what is plugged in. You probably won't drain the battery if it's like my truck everything turns off if the battery gets low.
Are your saying they are physically hot, or just active? If they are actually hot, temperature wise, I would be concerned. Otherwise the 12V outlets in my truck are active too, just like the Acadia, even with the ignition off. Seems normal to me.
All GM products that I have owned work this way. The power stays hot (i.e. "on") in the 12v outlets when the car is off. And yes, it will drain the battery if you have something plugged in for too long. I have a AC inverter that I use and if I leave it plugged in it will drain the battery over night. In my Montana, I installed a 12v solid state relay I bought from Radio Shack and made the 12v outlets turn off when the ignition was off, but I have not yet done that with the Acadia.
In our bonneville you can have it hot all the time or hot with just the switch. You can change it by the placement of the fuse. I have not looked on the acadia to see if it can be changed. Right now I know it is hot all the time, but that is the way I like it.
Yes the outlets are always powered and they will drain the battery if something is left plugged into them. Found that out the hard way after taking a week long vacation and I left the radar detector plugged in. :banghead: