Me & my wife are Brian!
Seriously though, I've got a plausible theory. Stay with me here, because the sheer bastardry of this is kind of astounding.
Let's say you're in a turf war over a big money item. Let's just say blue widgets as everyone loves those.
You're pushing by PPC, and so is your competitor. You've both got a few different landing pages saying why BlueWidget500 is better than BlueMaxW,, etc.
Now, you could attack the LPs... but why? Surely a big player will have other hosting elsewhere that they can mirror over to, and any marketer who's not an idiot will have latest versions of their LPs sitting on a disc at home. Or they could just steal the page from BlueManWidgetsGroup.
You could attempt to click fraud them, but it's really not going to do all that much...
So what can you do?
You can find a different network that also offers Blue Widgets Pro, move your traffic over there, and then attack the box that the payment gateway or tracking sits on for the network running regular Blue Widgets. Take out the entire network from underneath your rival... And everyone else pushing Blue Widgets. They're collateral damage, sucks to be them. Admittedly it takes a BIG attack to take down a good network, but anyone doing 5 figure days would have the money for hiring a few different bot swarms from all over the globe.
In the meantime, your competitor is losing out big time on acquisitions and paying money for the clicks, so it's lose-lose for them. Better yet, their PPC provider might even slap their account for sending massive amounts of traffic to a useless page, and the attackers ad will get shown more because of it AND you'll potentially be getting the traffic from the other smaller fish that you took down with your main rival.
So even if the network is only down for a day, you've still done a massive amount of damage to your biggest rival, innocent bystanders be damned, and you're reaping profit as the only game in town.
At least, that's how I'd play it if I were an evil cashed up bastard.
Any of the big money players and/or hackers care to comment on the theory?