I think the main reason they would hoard the FP's was because Disney didn't really enforce the time(s) you had to return in the past. Therefore, it helped their way of touring the parks.
I don't see it as abuse, just a case of doing your research and asking cms if they could return after the printed time, if the cm said it was ok, or would let you through, that's fine. If you don't ask, you'll never know.
Only 3 ways I can think of that one MAY be able to abuse the FASTPASS system.
1. I have read that the FP kiosks themselves have a button at the back of them that, when/if there is a problem with accepting someones card, a cm could press this button on the back and it would distribute a FP for that guest. If one was to look for an unoccupied kiosk or see a cm distracted at another kiosk, one could simply press this button at the back as much as they'd like and it would spit out FP's (again, only read about that, have no other proof so it could be a load of rubbish).
2. The cm who you give your FP to inside the queue area just takes the FP off you without looking at it. You could have a legitimate FP for say, Buzz Lightyear from 1pm-2pm that day, and take with you weeks/months/years of old, unused FP's for different attractions. Use the Legitmate FP to show the cm at the the entrance to the FP queue, then give the second cm one of your old unused FP's. Do it twice, wait for the cms to rotate and repeat.
I have never, nor would I ever do this, my apologies if I offended anyone with this point. It is merely to try and put my point across about the difference between abuse of the FP system and knowing how it works and using it to its fullest, whilst following Disney's rules/terms.
3. People printing off their own copies and selling them on eBAY.
Those 3 points to me, are FP abuse
If you are looking forward to FP+ then that is fine, and I totally and fully respect anyone who thinks that.
My worry is, as I have made in other posts, is that you make your booking for MSEP one night, and then it is cancelled due to the weather. That to me, is a wasted FP+ right there. I'm sure Disney will compensate by offering a FP+ for another attraction whilst the park is still open, but for some, they may feel that's not good enough.
What if you want to change your FP+ reservation due to a reason, you go try to log onto the disney app/website and it is experiencing 'technical difficulties', or the battery in your phone dies?
Again, i'm not attacking anyone with this comment, I appreciate and respect anyone who disagrees with me on this. I've found this thread to be a great discussion which has been done on peaceful terms