The New Yorker published a lovely piece by David Owen under their "Annals of Environmentalism" banner in the December 10, 2010 edition. (Subscription required for access to full article; abstract free.)
The article describes the Jevons Paradox, which postulates that improving the efficiency and thereby lowering the cost of a product or service will result in more of its use rather than less. The cited case in the original paper by Englishman William Stanley Jevons were efforts to improve the efficient use of coal.
Another English economist (Len Brookes) brought the concept back to the forefront during the oil crisis in the 1970s, arguing that devising ways to do more with less oil would result in higher energy consumption, not lower - a so-called "rebound effect".
Discussing this paradox and determining if it is valid is of critical import to energy policy and efforts to improve energy efficiency, so is of obvious interest to utility professionals in the EE field. I expect that IT professionals will be equally intrigued, given the tremendous rate of change in the performance and yes, efficiency, of successive generations of IT equipment.
It is not an unfair question to ask whether improving data center or IT equipment efficiency will simply make all IT capabilities cheaper, and therefore used more, and by more people, gobbling up any energy savings and attendant environmental benefits.
I've got the outlines of a paper (or perhaps a chapter in a book I am pondering writing) that specifically looks at IT and energy use and the Jevons Paradox.
In the meantime, if you want to dig deeper, I recommend this post from James Barret at the National Geographic website, and not only because he reached for the same Yogi Berra-ism that I did when first thinking about Jevons.