Celebrity deaths seem to always come in blocks of three: the most famous being the deaths of Michael Jackson, Farrah Fawcett, and Ed McMahon within 72 hours of each other. (Though for my money, Romeo LeBlanc dying the day before MJ could have also qualified)
Johnny Cash/Warren Zevon/John Ritter all died within a single week in 2003, and celebrity watchers were fearful when Shirley Temple died just a few days after Philip Seymour Hoffman.
Last Thursday we lost Richard Attenborough, and now today Joan Rivers. Is there a third coming? Or does Rivers reset the clock?