I think it's fine if that's how you refer to yourself in the context of hobbies, much like people would call themselves 'foodies' for example 'filmfanatics' (Or "Screenie" as someone once called himself), otherwise I find it amusing.
I guess it evolved from the social arc-types such as 'chavs', 'emos' and the like.
I just think self boxing is pathetic. I play games, hell I even run tournaments, but to think that these things define me is, at best, shallow thinking. Also, South Korea sucks at everything it does, especially rollerblading. Let's see who gets that one.