Most importantly, where will those $10M end up? You just distributed back to the economy a bit of money that was parked somewhere. That's good on it's own.
But that's a bogus argument. Just because a lot of really amazing technology once had it's naysayers or was called impossible, doesn't mean that when that happens for uBeam, it will necessarily, likely, or even possibly be the same outcome. Nor does it make it OK to invest in snake-oil because maybe the company might just "pivot" and make a zillion selling USB-3 ultra-sonic coffee grinders instead.
And that money can and should be invested in a much better way. The lines of distinction between uBeam, Theranos, and outright investor fraud are very, very thin.
You may as well defend an investment strategy of sending 10 million dollars each to random strangers on HN and seeing what happens. And I, for one, would definitely prefer this.
Of course that all depends on the founders actually wanting to build something that works, and not being a complete scam :)
Sometimes these bets payoff, the investors adjust for that likelihood. But it's not a game for the faint of heart.