Who is your favorite artist? Artist is a person.... who is used. What is your favorite ice cream flavor? Ice cream is an object... what is used.

就像Okaydaniel所说的，Who 是用在于‘谁’。What 则是用在于‘什么’。现在的年青人都用错英文。其实我也不例外。可能是习惯了或一时口快吧。