This is comparing pre-Christmas-day traffic to Christmas-day traffic. Many people spend December 25th doing very different things than they do other days of the year.
A good way to account for this is to look at year-over-year change. It looks like on Dec 25 last year, they took a 13% hit[1]. So it appears that their 60% hit today should be tempered a bit, to account for this. Even still, I think we can say that this is a very bad day for Rap Genius - especially when you consider that they have a lot of artificial publicity due to the currently unfolding scandal.
[1] https://www.dropbox.com/s/lidlugtdycdrrnx/Screenshot%202013-...