"These days, most Gmail users never even glance at the ads filling the right-hand column."
What sort of idiot writes that. I mean seriously. Do people really believe that Google just serves up those millions of impressions for the hell of it with no payback?
People look at them. People click them. Google makes a ton of money. Advertisers get a shedload of traffic.
It's an absolute douchebag move to mess with other peoples content. Reminds me of the free wifi services that inject their own adverts at the top of every page on the internet, or rewrite affiliate links etc. I don't care if this plugin is useful or not, I don't want it to mess with the DOM.