I suspect no one was using them anymore, if anyone ever did, but I have disabled the "iCalendar" links and RSS feeds for subscribing to site events. Badly behaved scraper bots were hammering those links, and for some reason they were very expensive to generate, so it was causing a massive load on the site and bringing it down for days at a time. Unfortunately I have no good way of specifically blocking the bots, because they constantly change their IP address and user agent. Fuck those jerks.