Flickr user VKKV

The Marsh Tacky Run was due to return February 2013, but has been called off after internal debate and, for official reasons of liability and safety. 

I'll point you to Tom Barton's report at The Island Packet; read it here.

The 2012 installment of the race sparked a heated debate about who was allowed to enter marsh tacky horses into the race, and the validity of the process used to discern which horses were truly purebred — the horses lineage is traced to Spanish horses left on the islands in the 16th century.