they are not going to donate until they try the tool and after they have done so they will probably just move on.
That's just it, the whole concept behind the Donate Button or a Thank you button has to be 100% impulsive, in that the user thinks great work thanks, clicks once to go to the donate page, chooses the amount frequency and confirms. All done in seconds, no need to give a site you do not trust your credit card details or even your name, it is totally anonymous and from that perspective risk free.
Something like this would only start to gather pace once it becomes more common.
Would I ever click on an ad (anywhere) - I doubt it. Would I say "Thank you" by offering a small micro payment to the site via G - definitely.
Google can make money from this by taking a percentage. Plus, imagine the press coverage as well, when if it were used for charitable donations by billions of people making micro-donations of just a dollar or a few cents. Wow.
I have never given to a cause like that but if i could do it painlessly, and quickly and for small amounts I am sure I would start donating.
Not many average Joes have AdWords accounts.
Maybe when Google's new music service gets going in a few months there may be a payment system that can be used to donate to favorite websites, charities, etc.
You could be onto something here. Perhaps music and micropayments for music will be what gets the ball rolling.
I just want to add that I see G just as the middle man, the innovative 21st century banker, the guy that stores my cc details securely and allows me to go to other sites and say "thanks for your info etc" or "I am not rich but I want to help" and that site gets some extra revenue etc.
If anyone can do this, G can.