Titanium needles only have a very thin layer of titanium on the outside of the needle. If they break, they do no more or less damage than a regular needle would.
http://www.superiorthreads.com/educa...coated-needles This explains it better than I can. I use and love titanium needles. Some of them have broken in my machine for the same reason a regular needle would with no harm done to the workings of the bobbin or the shaft.