It'd be safer to say "publisher OR developer". It'd be nice to think that development studios have our best interests in mind, but they have as much incentive to do the same things their publishers do. If they can avoid taking the heat, all the better.
"Having someone Tweet "YOU'VE BEEN SERVED" with a link to a PDF isn't that much different than having papers shoved into your hands at a crowded mall."
Not really, it's like giving someone a key to a deposit box with the papers in it. If you never actually posses the papers, even if you were aware that you had the capability to get them, it wouldn't be legit.
"Youtube can't do much to prevent this abuse. It has to err on the side of the rights holders, even if the rights holders don't actually hold the rights."
That's an excuse. All it has to do is allow rightsholders to file a DMCA claim, you know, the one that has legal ramifications for falsifying. If Google wasn't such a fucking loser when it comes to standing up to ContentID and DMCA abuse, that's the only way things would be handled.