Another reason Google or any company with large (and expanding) electricity bills might be looking at this or a similar strategy is the expected financial risk that will come with an effective price on carbon/GHGs. Being powered by high carbon sources like coal will be a risk, but also a relative opportunity for forward-looking companies to link their electricity to greener, lower cost sources (as you mention).

While I’m sure that Bill and others hear from many potential wind (or other renewable) developers when Google is looking at siting new data center projects, it’s difficult to assess what impact this is having on Google’s overall environmental footprint. The collective knowledge outside of the company is fairly scant on Google’s data center siting, and company does not take the fairly commonplace step of disclosing it’s own emissions footprint, via the Carbon Disclosure Project (like many others in the IT industry do) or other mechanisms.

For a company that is indeed leading the IT industry in many aspects of green tech (especially in their <A HREF=advocacy work), this is a specific place where Google can <A HREF=improve. This type of sunshine from the company would be able to confirm whether or not your thesis — that Google is actively attempting to power is data centers with clean energy — is indeed correct.