So you didn't "accidentally" hire people. You did it with a lack of foresight. To me, that's different.
Saying you accidentally hired people makes it sound softer than it really is. If Raytheon or Boeing hired 2,000 people ahead of a defense contract they were sure they'd get, and didn't that wouldn't be an "accident." That would be poor planning (counting your eggs before they hatch kind of thing.)
Either way, I don't really care either way about Zynga. I don't think I've ever played their games, but at the same time I'm not hoping they fail.
You are a middle manager. Do you say "bob in the other department hired 5 people, so I guess I'll stick with the three I have"? Nope. You go straight to your VP and say a rival VP just got five guys, where's mine. If hiring is decentralized and no one is concerned about costs you end up growing exponential.
That sounds like what would happen at Strawman, Inc. I've worked at a bunch of companies, big and small, and have never seen hiring justified like that.
Now, getting people and teams transferred once they are hired? That's a whole different story.
Then the VP is not doing his/her job correctly. Someone needs to be aware of the budget for salaries and be responsible for ensuring it isn't exceeded (and held accountable if it is).
It's also very backwards (government-level!) thinking to be playing the hiring quota game like that. I'd much rather hire a few members in a kick-ass team than participate in a headcount battle.
I could see two people both hiring a janitor without realizing it, but not "accidentally" hiring a lot of developers, designers or whatever else.