Well, it sounds reasonable to ask that question if so many people have Adblock installed?

I have always blocked ads and always (try) will be, but I this is the outcome from Adblock going mainstream. Yes, the ad networks/sites were the reason in the first place, but it doesn't matter. Another side-product is (hidden) "native advertising"... so many tweets/share/likes are purely marketing. That gay marriage article Madonna tweeted? Think twice before you believe he does it out of morals, most likely she is being paid to share that out with her audience.