I think some of those add/removes are just mistakes. Like moving your mouse and as you're moving it accidently click on the fav button. I know it happens. Though I do hope FA does remove the notifications that a fav has been removed. It is annoying.

When you put it that way, that could be it maybe...

-nods- If it's just fav and then unfav quickly. then that's probably it. If it's fav and then unfav a day or more later. Then it's someone that likes keeping their favs neat or down.

Yeah that happens sometimes when faving and unfaving by accident.

sometimes people click too fast when FA is being slow, which causes the unfave notification to appear (possibly several times).