For me, all of the above. I am traveling alone.
Just because more than one person has an AP does not mean they must book separate rooms although they can if they wish. Only one person has to show an AP to check in.
Once I checked in with my AP rate and they didn't ask to see my AP. But I had been to a park earlier that day and perhaps the resort computer system pointed that out as verification I had an AP.
Disney hints:
http://members.aol.com/ajaynejr/disney.htm
I got a WDW AP rate on an airplane ticket! (you could say)
Jan '03. I was at WDW and bought an AP (premium).
Had I not bought the AP I would not have gone into Disney Quest for an hour almost evey day.
Had I not gone into DQ on one day I would not have logged onto the internet and found out via The Dis that Delta offered some low fares for the dates of my next trip. (Indirectly. Someone pointed out that Delta changed aircraft for the route and typically when they do that, a few low fare seats re-appear.)
Had I not booked then and there (running up the stairs to the pay phone since the internet station wouldn't go to the booking page) those low fares would have been gone by the time I got back home.
Unfortunately I forgot to book the Comeback Rate (short lived discount promotion where you book your next stay before leaving WDW) for my resort stay so I am stuck having to call back every now and then to see if more AP rate rooms open up for the dates I want.