[Steuard]

I know nothing about their theories, clearly. But if I had a nickel for every suggestion I've heard for somehow extracting energy or momentum or something useful from quantum vacuum energy, I'd have, well, a couple bucks.

The thing is, we've already got some awfully good theories about gravity and inertia, and a lot of their predictions are very well tested. Just as one example, if these folks think that what they've been working on is "a possible alternative to the Higgs" (a quote by Haisch himself in 2006 on the Talk page for his own Wikipedia entry), doesn't that mean that the actual recent discovery of the Higgs (and its good agreement with mainstream theory) strongly disfavors their alternative explanation for inertia?

There are too many fringe theories like this for any working physicist to have time to refute them all in detail. (I did my time years ago, trying to refute the nonsense of "Heim Theory" that had a crowd of Wikipedia proponents and a few overly credible mentions in the popular press.) At some point, when people start talking about replacing the foundations of modern physics you have to be skeptical, and raise the bar quite high before they merit serious attention.