I'm actually familiar with several fanfic writers who have made the leap to commercial publishing. One of them with a recent publication is Maria Lima ("Matters of the Blood").
The reason a lot of people read fanfic is because it tends to be better written and, often, more interesting, than the crap that passes for "professional fiction" nowadays. In case you've somehow missed it, I'd point you to the craptastic yet (somehow) critically acclaimed "Voyage of the Narwhal" by Andrea Barrett. From a purely technical standpoint, for example, in one chapter she spends 3 paragraphs in the cook's point of view in order to tell (not show) the reader what the captain is feeling. This is not only bad writing, it's lazy. My 12 year old could write three paragraphs from the captain's point of view and "show" me what he's feeling without having to resort to a singular, unnecessary, and rambunctious point-of-view shift.