As far as I remember, it was the increasing vulnerability of the site (not just to spam, perhaps) that was the trigger for the closure of Henneth Annun. But Henneth Annun was relatively unusual in being hand-coded, but automated, so had different technical challenges. Also, a number of options were considered and discussed at the time, including freezing the site. HA had already been on a slow downward spiral for some time. Part of the site did stay up, of course, but not the fic.