hehe well if that was the case rice fields would always have dead birds. And besides bird seed expands much more then rice does, and you don't see any dead birds from that. So there is no harm to them eating some rice.
Anyways the actual reason why rice shouldn't be thrown at weddings is for the safety of the people walking around. So that people can't slip on rice when they walk on sidewalks or other smooth surfaces.
Hmm i think it's usually raw, but i think either one wouldn't harm the birds. They are pretty good at digesting foods like that.
And yep that makes sense to me as well. Since i guess it would be like stepping into a room with a floor covered in marbles. And the wedding party wouldn't want to get sued. So best to not throw rice.