If I may be so bold, the point is not allowing non-fannish types to post there. They already can, if they write something lj fandom considers fannish (even if they don't consider themselves fans--though, er, why would they want to?). The point is that there are already fannish types for whom the fandom experience also has original works with fannish sensibilities.

I personally really doubt we will be deluged with non-fandom people posting stuff. What it could happen is that fandom people post more original stories than other fandom people may want.