Sure if you are the type who would kill NPC for supply. Throwing knife isn't as rare as you make it out, but rather common for all general vendor.
Another significant trait of throwing knife is that it is a conceal weapon which you can carry into casinos.
"rather common for all general vendor."
Wow, there are so many things wrong with that sentence. They aren't "rather common", and they aren't sold by "all general vendor(s)".
You are the first person I have ever heard say that. As far as I know, Mick and Ralph, Chet, and Cliff Broscoe will sell them. Chet and Cliff sell them occasionally (usually 1 or 2 at a time), while Mick and Ralph sell 15 when you first open up the special inventory, and then rarely ever sell them after that. Most people I've spoken with agree the throwing knife is considered overall to be 'rare', and I think we (at least I) have played the game enough to visit "general vendors" a few times.
It could just be my game, since now there are 7 vendors I know off the top of my head that have stopped replenishing their stock of all inventory, but even when Mick and Ralph did have new stock in, they would rarely ever have Throwing Knives, and when they did, the most I ever saw was three.
If you want to share with me where you are getting this bountiful supply of throwing knives, please actually give me a name and location. Saying "the throwing knife is common" doesn't prove your argument. You need to prove it to me by providing at least a bit of evidence. I would LOVE for you to prove me wrong, since I always play as a ninja character. I've made multiple topics on these boards regarding stealth assassin play, and am dieing for you to prove me wrong so I can finally have many throwing knives.
http://fallout.wikia.com/wiki/Throwing_knife_%28Fallout:_New_Vegas%29