[Wongboy]

My personal experience is that bad/new players make mistakes with all stack sizes, but their more costly mistakes are when they are playing with large effective stacks. With small effective stacks, they play speculative hands, and with large effective stacks, their calling station tendencies take over. For these players, they are in the danger zone when they get a big stack (and should strongly consider leaving when this happens).

More experienced players usually know not to donk off a big stack, but they will still frequently fail to adjust to a smaller stack and will still play speculative hands when their opponents stack size is not large enough for that play to be profitable. For these players, their mistakes will usually come when they have a big stack, but there are several small stacks at the table. Of course, those mistakes are less costly than misplaying big effective stacks.

Note that big stacks can also choose to play sub-optimally against a small stack if there are other big stacks in the hand. This is the nature of the inherent advantage that comes with a short stack, and is not usually a mistake on the part of the big stack.