Wired News has picked up the eco-friendly data center theme in a story by Amit Asaravala, who looks at "green hosting" as a niche play that offers pass-through appeal to clients. He correctly defines environmentally-friendly data centers as a non-standard practice that is viewed as impractical by most major providers, and thus unlikely to emerge as a serious trend within the industry.
While I draw distinctions between solar-powered data centers, there is a small but potentially sticky niche for hosts that "walk the walk" and impress customers with an authentic commitment to the environment. Consumers whose buying decisions are influenced by their environmental beliefs will likely have strong brand loyalty, which has significant value amid all the churn in the web hosting industry.
The growth potential in green hosting is likely to be found in the reseller space, where hosters can take advantage of the niche appeal of eco-friendly hosting without the complexity of running an enviro-friendly data center. Of the providers who appear to actually operate their own green data centers, AISO and EcoSky have reseller programs, while Solar Data Centers offers only a one-time referral fee.