I started writing this story in part because I'd bogged down on a book I was working on (now debogged), and that means my top priority was to have fun writing again.
If whoever downvoted this would like to explain why, I'd be interested.
(General consensus seems to be that HPATMOR is in fact an exceptionally good instance of Harry Potter fan-fiction. It therefore seems likely that most people are not as good at writing Harry Potter fan-fiction as Eliezer is. Ergo, his success in getting more visitors to his site by writing Harry Potter fan-fiction is not likely representative of what other people would achieve.)
I started writing this story in part because I'd bogged down on a book I was working on (now debogged), and that means my top priority was to have fun writing again.
It might have helped in other ways, too. Release of this fanfic correlates with increased traffic on LW: http://siteanalytics.compete.com/lesswrong.com
Apparently if you want to get more people to visit your site, write Harry Potter fanfic.