Matthew,
I'm a "Knife Thrower" but probably not by your definition.
If you mean that someone has to throw in the vein of "Professional Style," etc., no. He nor I probably are.
Speaking for myself, it is for relaxation and skill development. With an eye towards using it as a potentially damaging tactic for Self-defense.
I think there is a distinct difference between Sport Throwing and Self-defense Throwing, and that is without bringing in all the baggage that many do about throwing your Primary Weapon. I carry more than one knife.
I even buy cheap folders and chuck them sometimes too.
So, Combat Throwing of Edged Weapons or Any Improvised Object for success, cannot depend on specially designed throwing weapons with "proper" weight to overall length ratios.
You have to be able to throw anything.
I actually enjoy throwing CS Vietnam Tomahawks and Estwing Hatchets even more than knives and I do own a "Throwing Knife," one of the best I have ever seen in terms of toughness...
A Bowen Thrower. This thing is a Heavy Duty CHUNKER. When it hits, you hear it really good, if you know what I mean. It makes throwing a knife a pleasure.
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"You are no more armed because you are wearing a pistol than you are a musician because you own a guitar." ~Jeff Cooper
And the same goes for a knife...
And, I'm a Usual Suspect.