For my stand about this as an amateur fashion blogger/fashion enthusiast, I don't purely believe that Tumblr or any internet sources is killing personal style. I guess, tumblr and internet sources are more like general guidelines. People look over the internet to look for inspiration. To keep them guided from what's in and what's out. You may have based your look on what you saw but still there will always be a little amount of you in what you wear. You may have followed different fashion blogs to look into but that doesn't mean you don't have originality. Combining those different blogs will sum up to you which is another new product. And, that's what you think who you are. It's like you've created an innovation from an existing fashion lines by combining them and through your own self-expression.
But mind you, imitating is a different story bro. I believe that you can be better than that. Just be guided from what you've seen. After all, fashion is a vast universe to explore. There are a lot of enigmas to it.
I am Paulo and that's what I think.