I think this has been a very popular business practice lately, and it's very beneficial from both a financial and marketing perspective. Data centres for large companies can cost quite a lot of money to run and maintain. When you figure in power consumption, redundancies, backups, and even the physical floor space needed to house all the servers.
Beyond that, some of the more innovative companies out there (and I'm proud to say the one I work is one of them) are exploring powering data centres using solar/wind generating stations built directly at the site (where feasible) i.e. solar panels on rooftops, or windmills on adjacent land.