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The Energy of Empty Space != Zero
Raindeer writes "Lawrence Krauss (well-known physicist and author of The Science of Star Trek) invited a group of 21 cosmologists, experimentalists, theorists, and particle physicists and cosmologists. Stephen Hawking came; three Nobel laureates, Gerard 'tHooft, David Gross, Frank Wilczek etc. He wrote about the conclusions of this session in Edge; in short: 'there appears to be energy of empty space that isn't zero! This flies in the face of all conventional wisdom in theoretical particle physics. It is the most profound shift in thinking, perhaps the most profound puzzle, in the latter half of the 20th century. And it may be the first half of the 21st century, or maybe go all the way to the 22nd century. Because, unfortunately, I happen to think we won't be able to rely on experiment to resolve this problem.'"
Zero-point energy is predicted by both the leading quantum physics and relativity models. This is like 70 years old.
The Casimir Effect has been observed/measured.
Here is a this very nice discussion of the zero-point energy by mathematical physicist John Baez. You're right, the idea is hardly new, but some of the experimental evidence about the cosmological constant is relatively new.
I think it's fair to say that almost no physicists believe you can extract useful work from the vacuum energy. Most of the people claiming you can are con men trying to swindle people into buying "free energy devices" that supposedly tap the zero-point energy (it's the modern day incarnation of perpetual motion machines). While you may be able to setup a situation where the vacuum does work (i.e. with the Casamir force), I think it is simply less than or equal to the energy it took to put the apparatus together. Essentially, it's equivalent to sitting in a room with uniform atmospheric pressure and trying to use that atmospheric pressure to do work. You can certainly use a vessle with low or high pressure to do work, but you're never going to get out more energy than it took to create that high (or low) pressure. While one can think about this in terms of thermodynamics, that's really litte more than making concrete the common-sense proposition that you can't get something for nothing. Thus far, nature has not given us any good reason to abandon that idea.
Sometimes people do talk about things like pair creation from the vacuum and the energy-time uncertainty relation, but they are speaking about virtual particles rather than actual particles. The bottom line here is that when you make a measurement, what you will find is actual particles and energy will be conserved, even according to quantum field theory.
"You call it a new way of thinking; I call it regression to ignorance!" -- Operation Ivy
What you've just described is commonly known as Maxwell's demon, and is thought by most physicists to violate the Second Law of Thermodynamics.