I like the idea of giving users a painless way to donate to the sites they use. And giving thank-yous in place of advertising is a good way to reduce the incentive to freeload.

I do worry that $1-3 a month is much lower than the value I get from the sites I visit, and consequently not enough to support low-traffic sites that should be supported. They also didn't mention how they distribute your money - equally to all the sites you visit? Proportionally to the number of visits? On a related note, can participating sites choose to eliminate ads only if a user will contribute enough money to them, or must they eliminate ads for every contributor in order to participate at all?

But the real question is, will google.com itself accept Contributor money? And will it eliminate ads for contributors?