Well, Doug, the use of helium in BMWO's hull was proposed on Sailing Anarchy by TonyF18 in November 2009, some time before it 'broke' here. And there's a link back to a patent using helium for sails in 1979. Both of those points once again underlines the fact that it's not a novel idea; merely one that is not practical enough for most sailors to care about.
Hmmm, let's see; I buy some ultralight bladders, get them inside my cat hulls (which will have to be made with even more care so that there are no sharp edges from 'glass, bolts etc) and drag down a bunch of heavy bottles every now and then, all to (perhaps) gain a few seconds around a race course.
Expense for the whole fleet has gone up, hassles have gone up, and we either get to re-set the course a fraction longer, or get to do less sailing.
This does not excite most people. It's a disproportionate cost and it is NOT a novel idea. If we want to go quicker, there are many ways. We can adjust courses to have more reaches. We can no race in light winds. We can add taller rigs and wider wings or platforms, and accept the considerable loss in ease of sailing and practicality. We can hire motor cruisers to go around the course in front of us, crushing waves that would slow us and (when necessary) making wakes for us to surf. We could start each race under tow from a V8 skiboat. We could pump, furiously, when underpowered. We could sell our Lasers, Flying Scots, Formula boards, Hobies, 505s and Melges and all buy C Class cats and fit them with kites.
In other words, there are already a gozillion ways for the average person to go faster under sail, but almost no one cares to take them up, because sheer speed is not what most people are into. We don't want to add complication.