It's such a ridiculous statement, too. With his logic this guy would have to buy the cow that makes the milk he drinks in his coffee...
Nobody forces you to buy a cow to put milk on your cofee, but if you go around offering "organic capuccinos" for sale, your customers could normally expect you to either milk the grass fed cow yourself or, more likely, purchase your milk from a certified provider that does so. They certainly don't expect you to claim that since you make a donation to some Amish charity in the other side of the country, you are entitled to slap a "organic" label to the same brand of industrial milk your competition next door uses and offers at half the price.
I don't see how this should be any different with Google.
Let's say for the sake of the argument that Google's datacenters consume 1% of the electricity in the US.
If Google were operating its datacenters with clean/renewable electricity produced on site, it means the technical problems are, for all practical purposes, already solved; and now everybody can just license their technology an imitate them. There still remains the economic and political problem of having the other 9x% of the country to jump on board, and invest the required resources to convert to renewables, but that's simply a matter of how much money is devoted to that. It could take us 100, or 50, or 20 years, but we'd know for certain that we will eventually get there.
Instead, we have Google claim to be operating their datacenters with clean energy, but instead they operate with whatever mix of clean&dirty energy is available from the local provider, and then go elsewhere and finance the production (let's say, same amount of kilowatts/hr) of renewable energy. That is still a good thing, since those investments would never had been done without the incentive, but there are 2 problems with that.
1. You call electricity "fungible", but it is not. You cannot generate the same amount of solar kWh per dollar in Alaska than in Arizona, the same way you cannot generate the same amount of hidro kWh/$ in Arizona than in Mississipi. By following economic rules, it is rational to assume that Google is picking the low hanging fruit first. Therefore, when the other companies try to emulate, they will find that the second 1% will be more expensive than the first, the third than the second, and so on...
2. The other big whale in the room is that renewable electricity, unlike coal-based, cannot be produced on demand. Until the problem with storage is solved, - and for what I have heard from people that has been doing this for many years it is far from solved, - you will need some form of fosil fuel to close the gaps when production is low. It is very easy to add 1% renewables to the general "fungible" pool of electricity in the grid, but 5% would be less so and I don't think it would be possible at all to do 50% with current technology, even if the production capacity was already in place.
So, what do you think? are my concerns really nonsense, or ridiculous?