kbaby, my DS has been a determined thrower for ages, he's now 3.5.
I think on this one, pick your battles. My DS knows that I will be very cross indeed if he throws near other people and that if he breaks a toy, that's the end of that toy. But it is such a strong compulsion I don't feel right stopping him throwing his toys all the time. They are his and he has to learn caring for them appropriately, which he can only do by experience....obviously you mustn't put up with your DD throwing plates, I understand that, but can you sometimes bear with her if she's throwing things that aren't going to break or hurt?
It's just part of his make-up - in fact from our venture photo session, the best photo and the one that captured the essence of him at three years old, was of him laughing his head off, arms raised up and a toy above his head!!!
We have balls, and toys to throw in the garden and he has his freedom there. He has learned to throw more appropriately and I'm sure your DD will too, it is definitely a 'stage' and she won't do this forever!
However I am extremely tolerant, I know that, and put up with some things that others couldn't bear..just thought I'd respond as I know where you're coming from!