That's missing a number of points, both historical and behavioral. Digg.com died when they tried to increase ads and there was a mass exodus from Digg to Reddit. Additionally, even if only those 2% leave, you're still screwed because those 2% produce all the content/share all the links that the other 98% want.

Rule of thumb: if you're business is selling your users to advertisers, don't piss off your users, because then you'll have no product.