I voted you up, but I disagree to some extent.

I expect that if you're creative, dedicated, and put in the time to tackle the "long, hard slog" you'll have something of considerable value by the end of it. In fact, if you can get the momentum necessary, you'll have precluded others from even entering the field.

But you're definitely corect that the right persona and pre-existing followings basically super-jumpstart these types of sites.