I think one of my biggest peeves are young 'anime' artists. Don't get me wrong, I Love anime, manga, and all their stylings; but you're never going to be able to draw in that style correctly if you don't learn how things actually look first. I mean, how do you think the first artists developed their styles?
Plus there are lots of other great things you miss out on when you decide you're only going to draw anime. I mean, would you really want to cut out influences like the timeless Calvin and Hobbes, thrilling Batman, classic Disney, or beautiful Ernest and Celestine (to name a few) just to become another indistinguishable mangaka? It's just.... Depressing.