What is the longnest blockchain fork that has been orphaned to date? On this thread, the user asked what is the longest unintentional fork that Bitcoin had suffered. From the answers present, Bitcoin never had a >4 block fork until 2012. 

It has been 6 years though, and I wonder if there is a more up-to-date statistics on that question, and if any study has been done so far.
11/12 March 2013 Chain Fork at block height 225,430.It's 31 blocks long.