I too am perplexed on the 'implosion' thing. From what I've read...my take is that when H's and O's are mixed and exposed to spark/flame in the exact ratio of water (2:1), they rapidly return to their original volume (implosion). See, as gasses, the volume they occupy is something like 1600 times larger (forget actual no., please feel free to correct) so when they slam back together to form water again, it creates this vacuum. This is the operation of Yull Brown's Gas, like in "water-welders". Steam expands to something like 54X's original, but it is still really water. Just fluffed up with lots-o-heat energy. I think it's the same principal, only instead of heat energy, you use electrical energy to fluff it up but to a much further degree-- STILL JUST WATER, but HIGHLY CHARGED.
I think why we don't see this, is our gas mixes aren't that clean, or at the perfect ratio. Might have some OH's, some H-H's, etc.. in there and instead of a perfect reconstitution to water, we get violent exothermic bangs. But hey, that's what I'm looking for!