On May 21, 2015, wikia user Hayashi-chan suddenly ceased all activity after answering a question. In the past she has been a fan of one wikia member's work of a crossover that we know today as Dork Diaries.Now, the guy who made that one is disappointed.
This isn't the first case,really. Users like Rebun123 HAVE made blog posts about their departure, but never told us when. As you can see, people can leave with or without warning. It doesn't depend on us. It depends on them.