Re: Same here
"But if y% were so pissed off that they made a mental note never to buy that product the net effect is actually x-y% and that could very easily be a negative number."
Back in the 1980s when I looked at this, advertisers reckoned that the really annoying adverts (Colgate's australasian "Mrs Marsh" ads being a classic example) caused the product name to stick in people's minds long after they'd forgotten the negativity.
Of course if you're feeling like a "right evil bastard" and have b/w to spare, you might setup something to repeately drag down as much advertising as possible to drive up their bandwidth costs and/or click charges.