Affecting Human Behavior While Preserving Choice

I came across this today - this is an area of interest to me, which is how to get people to make better choices without limiting their options. This book which deals with the mechanisms behind this, namely how to offer choices to people but to "nudge" them to make the best choice:
Things like getting people to opt out, instead of opt in, to 401k plans, or using dashboard indicators to let people when to shift gears in a car to get better mileage. The authors apparently discuss product placement, etc., and the psychology behind this.
As an extension, a couple of Harvard researchers have built a site based upon principals they've studied (and appear in a book): Seems very nicely done, and follows many of the principals discussed in the book.