But is any of it enough? I don't think so. The bigger question is, Can anything be enough to thwart a blight in a monocultural environment?
The real answer to the link devaluation problem has to come from outside Google. We need polyculture: for search, for advertising, for everything. In its absence, we get some fine but isolating services. And blights that take advantage of that isolation.
This circular Google-conomy is coming under scrutiny from left and right, because there's an apparently irreconcilable conflict here. The splogosphere that gums up our search works, colonises our referrer logs and steals our (well...your) content is a benefit to the adsense half of the circle. More places, more ads, more clicks, more $$. In the meantime, though, the legitimate content / hosting half of the equation is getting hammered, to such a degree that pretty soon no-one will visit or link in, & then no-one will see the ads, unless they're trolling for them. What had been the bright white shiny mega-mall in the 'burbs will have become the weedy lot with the empty stores, & we'll all be searching using some other service.