User blog comment:Rappy 4187/Technical Update: August 19, 2015/@comment-4129195-20150821143607/@comment-5275700-20150821151718

The "why" of any unexpected issue is usually a unique and beautiful snowflake (though my colleagues in Engineering would probably use more harsh words). The troubles in the last 24 hours were related to the ongoing (and previously mentioned) server-side changes to user preferences, and the specific cause is being investigated further, of course.