I don't think we've had mass partner death before. That's exciting! I guess Appmon had a lot of bullshit to make up for, so it makes sense to pull out something like this. Without getting into any of the conspiracy theories... I know they were going to kill the AppliDrivers anyway, but it was kind of dumb of the Ultimate Four to hand the AppliDrives (or at least Haru's) back to the humans first. That'll come back to bite them in the ass.
Their was the ending of Xros Wars: Boy Hunters, where everyone except Tagiru and Arresterdramon and the main heroes from past series were killed by Quartzmon. Well they became a part of him, and were still alive within him, but I guess that sort of counts as being dead and having mass partners and characters all killed at once. Also like Jay mentioned, all of the Digidestined and their partners from season 1 were digitized by Apocalymon, but I know what you mean rather exciting and sad at the same time. I thought they would smash the AppliDrives to pieces, made no sense for them to keep them or have them handed back, but I'm sure they'll use this as a way to introduce the AppliDrive DUO, either Denemon will upgrade the old ones, or they'll just magically transform into something new (a la Savers).
Apocalymon kills all of the heroes at once way back in Season 1. They get better because they've grown up over the course of the whole season (and the emotional powers they represent apparently allow them a one-time reconstitution from the Singular Zone?), or it could just be deus ex machina.
Either way, I think Appmon allowing the sacrifice to carry over to the next episode and giving the kids a chance to grieve is a much better way of handling the concept for maximum drama.
Whatever Yuujin's fate ends up being, I gotta say that I'm psyched for it now!
Something amusing that came up in chat:
All of the Applidrivers have names that transliterate to English names:
Haru=Hal
Rei = Ray
Eri = Ellie
Yuujin = Eugene
Asuka Torajirou = Astra (amusing that the foreign kid actually has the most Japanese name)
Naito = Knight
Ai?
Watson?
It's so frustrating that Appmon isn't getting a proper dub because it would be the first time that a dub wouldn't have to make up stupid English names.
Hal for Haru? The name Hal reminds me of the dad from Malcolm in the Middle, I'd bet they would go with something like Harold if they changed it. For Eri, I think they would go with Erin, I'd cringe though if they added an extra letter and call her something like Karen or Carrie, and Naito my guess would probably be called Nathan (This is all joking of course). Since Astra is his madeup name anyway, the dub could just call him Astro, and he'll say something corny in the dub like "I'm the star of AppTube, so just call me Astro." idk. Hmm Watson? Maybe Walters LOL!
Well with the way Tri is going who knows how this might be dubbed, but then again different audience, different standards, etc.
We've had characters whose names were changed when the names weren't Japanese to began with too you know. Like Dingo to Derek, Wallace to Willis, and Chichos to Rosa.
Plus, it's not the dubbing company that changes the names in the first place anyway, that's typically done by Toei or Bandai of Japan.
Chichos in Spanish means love handles, and in Mexican slang it sounds like chichi's which are the breast of a woman, so I'm not suprised her name was changed to Rosa. I haven't watched the 02 dub in Spanish in years, don't remember if she was called Rosa there too, they typically went with the American name changes.
It was a mere innocent joke, I'm not that kind of people that hold grudges or something. I'm watching Digimon to entertain myself and I'm probably one of the very few people that like all of Digimon seasons, including Young Hunters, Tri and Frontier. I enjoy Appmons as well, otherwise I wouldn't post various theories about its plot and characters. So, no reason to feel guilty or something! 
