October 2, 2012 off the Golden Gate - a Westsail 32 had to cut away her mast and rigging and motor back to port. " It was the T-bar on the backstay turnbuckle at the lower end. The T-bar broke away from the threaded part."
I believe that what broke is illustrated below. Note the crack in the T-bar probably from crevice corrosion.
Here is what happened when Pygmalion broke one of the above on the stb boomkin stay in 2009.
The boomkin's split and were driven into the cockpit - just missing this writer. We didn't lose the almost new mast but I almost got speared.
Once again check your rigging for these devices and remove them - Bud has great prices on replacements - much cheaper then replacing the mast, boom, sails, rigging, bow pulpit etc etc.
Jay
Here is a picasa album of other scary items to check.