The way I remember it is that, before Adsense, lots of websites used terrible ad networks based on popovers, popunders, impossible to ignore flashing animations, etc. etc.<p>The situation greatly improved AFTER Adsense made it more remunerative for most legitimate websites to run what were originally text-only, non-invasive ads. Yes, with tracking, but much less annoying.<p>My impression is that falling CPM revenues are bringing us back to how it was before Adsense.