Hi,
I used to juggle knives and clubs and did throw them a little a long time ago. The one thing I would say is that holding the knife by the blade is probably not a good idea. Stage show guys do it because it looks flashy, but if the knife is well balanced there would be no advantage to doing it that way. And there would be one (or two) serious disadvantages.
The obvious one of course is cutting yourself. Not knowing a lot about side shows, my guess is that they don't have to worry about that because the blade will be blunt along its length, only sharp at the point. But in the real world a knife like that would be useless.
However the other thing that makes me think it would be madness to throw that way, is that the knife is completely useless in your hands just before you throw. So when you're approaching the enemy, you surely want to have the knife ready, i.e. hilt in hand. Then to throw if you throw it by the blade you have to engage in an extra action, slowing you down and potentially alerting your target, where as if you threw it by the hilt you don't have this disadvantage.
And worst of all, what happens if someone leaps on you just as you're about to throw it? If you have the hilt in your hand, you have a usable weapon. You simply point it at the enemy. If you have the blade in your hand, you'll lose fingers trying to use it.
Cheers, Greg.