Here's a discussion of transportation and efficiency.  (link) His conclusion at the end is dead on:

"The crux of the transportation energy problem is that there are just too many people doing too much travel. The development and improvements of the motorized modes of transportation have enticed people into traveling more. The increased travel (and increased population) in the 20th century not only canceled out the 5-fold gain in fuel efficiency but increased fuel consumption for travel 40 times. Thus, in addition to striving to increase fuel efficiency, it's even more important to strive to reduce the need for travel as well as to reduce population."

Bingo.

Bingo is right, TRE.

The "how often you do X" multiplier is just as important as the "how efficiently you can do X" factor, and it's often the easier of the two to improve by a given percentage.

This is why I've been saying for some time that one of the businesses that will boom like crazy in the coming years is anything that lets businesses substitute virtual meetings for real, in-person meetings with distant people.  There are many solutions that do this already, of course, but my feeling (based on my years as a programmer, computer consultant, and technical writer and editor) is that it's still a new and immature technology.  

It's getting to the point where meeting in person is more about inertia than about necessity. We're no longer waiting for a silver bullet; the technology is already there in several different ways. Email, IM, teleconferencing, videoconferencing, video streaming, secure network traffic, and so on. Most of these technologies are pretty darn mature. You can't get by without EVER flying around, because face time is important, but companies can reduce the frequency. And they are doing so -- but slowly.

The sticking point right now is probably the human factor. Adoption is always slow to spread. Part of it is just time; you need the old guard to move on so that the new guard can adopt these technologies.

I agree with this. I co-founded a non-profit that's been pretty successful (http://crnano.org) given its small size and funding. I met my co-founder online when he wrote me about a paper I'd written.

The first time we ever met in person was more than a year after we started CRN.