Maybe not true ill-will most of the time, but metagaming is almost always an attempt - intentional or otherwise - to gain an advantage over the game.
I disagree. Because isn't part of the whole game trying to make good decisions, and trying to avoid death for your character? So it seems to me that beating the game, or getting an advantage over it, is part of the game's goal (along with just having fun, and an exciting adventure).
So this is where I think Iserith is correct to point out that metagaming seems encouraged by the game, because we all want to win don't we? Now of course there is a big difference between cheating (by for example reading the campaign module) and just thinking like a player.
In the a fore mentioned evil crone scenario, a perfectly good justification could be given to distrust the old crone, even if the players are also leaning on their knowledge as players regarding the fate of their rogue friend. I don't see this as ill intent. Everyone at the table knows the crone is the villain, so should they be even put into a position where they have to fake ignorance and walk right into the crone's trap?
And I think perhaps a more important question could be asked: Does it really matter if the players act upon their knowledge that the crone is a villain? So what if she doesn't drop them into her dungeon... what does it matter? Why make a big deal out of it?
In my opinion, the players should play their characters however they feel their character would act in the situation. Me knowing the players know what happened to the rogue has no bearing on what the characters know, so if the characters are just doing things they could do with what knowledge they do have - such as be very suspicious, and even assume wrong-doing on the part of the witch, up to an including guessing correctly about what exactly went down - I don't see any problem. They know the rogue went off alone and hasn't returned, so even if they don't know where the rogue was going they have an explanation for their worries.
But that is where I keep finding disagreement with this old definition of metagaming - people let knowing what the player knows distract them from even considering that the character didn't need to know it to do what they have done.
And again, I think more importantly I don't see why busting the crone on her obvious betrayal would be such a big deal to some DM's. Yes, the players could come up with plenty of reasons why their characters might suspect foul play. But even if they don't have a reason to suspect her, why even put the players in such a position where they have to completely ignore what they know as players? To me, there are many ways to avoid this issue entirely:
-Make sure the players don't know what happened to their ally, by revealing the outcome after they have had their encounter with the crone.
-Allow the players to act on their knowledge as players, using what ever in-character justification they come up with. And just don't worry about it.
-Give the PC's an obvious clue to the witch's betrayal, which eliminates the need for this strange game of pretend entirely.