When was the last time you saw a web site that wasn't selling something? Can't think of one? Neither can I. Every site I've been to in the recent past has either been directly selling a product, offering to trade something you have for something less valuable that they have, or showing you advertisements (either fixed or adsense).
My first thought on the recent overabundance of advertisements was "When the hell did everyone get so greedy?" At what point, did content get bumped to second-place behind ads? At what point did we start to not only tolerate ad-filled sites, but to accept them as the norm? That thought, of course, was followed by "Damn... I've got to get that ad-blocker plugin for Firefox..."
As a server administrator (that's part of my day job), I know that hosting is expensive. I know that shared hosting rarely works out once you've got enough visitors coming to your site to pay for it. I know that Virtual Private Servers (VPS) are overpriced and often perform worse than the cheaper shared hosting does. I know that dedicated server hosting generally means that you either need to be a server admin yourself, or that you've got to dish out a few hundred dollars per month to hire someone to do the work. I understand the problem. What I don't understand is why the perceived solution to that problem is to fill your web sites with tons of advertisements.