some ads are payed for on a per-impression basis. they have a CPM, cost per mille. or cost per thousand times the ad is seen. In those cases adblock does in fact make a huge difference as the ads are not being loaded and there are fewer impressions resulting in less profit. If I remember I think Bishop said in another thread that the ads on NS generate revenue based on their impressions, it doesn't matter whether they're clicked on or not. Although I'm sure clicking them generates even more.