User blog comment:Care Level/On Anti-Snowball, 2v1, Melee v. Ranged, and player satisfaction./@comment-8506165-20140715094724

"De-stacking" or negative stacking items sound impossible to implement in a way that would serve their intended purpose (leaving aside the idea that items that directly penalise you in some way for doing well seem a bit iffy to start with).

Playing against an opponent and they get a negative stacker? Well, either that means they can take you now, or you'll still be winning but just not quite as hard. If they can take you, then their item becomes less effective and then they can't do it. Unless the fall-off for these items is quite low, but then you'd just see people picking up one of their own if they see their enemy getting one, because it'll still be good after a few kills in lane. If they still can't do anything and you're still kicking their tail... well, they're not relevant anyway, then, particularly as they've sunk gold into something that's not going to help them transition into mid/lategame.

And of course, a few obvious abuse cases, even assuming the above problems are avoided:

You know that who barely even bothers fighting champions and just sits on your turrets all game? Yeah, imagine him with one of these.

Conversely: You wanted to play I think not.