All of my experience with broken frames (4) and broken parts have been with aluminum parts tearing more than fracturing. Both of the aluminum frames I've broken complained before breaking and then gently broke. The same has occurred with aluminum rims and crank arms...lots of noise than then they slowly tear apart.

Both steel frames I've broken have gone 'Plink!' and fractured like most people would expect aluminum to do. Pedal spindles have done the same thing as have all the spokes and hub axles I've ever broken. None of them have given any kind of warning like aluminum does. This make sense if you think about the material. Steel is really stiffer and springier than aluminum. It should fracture rather than tear.

Now Geosammy's frame is broken. It probably makes a lot of noise...creaks and groans...while he pedals. At some point, the crack is going to reach a point where the weld will separate but I doubt that it will be a sudden release. The lower tube will probably buckle and bend...although it could be cracked too...but I doubt that it will be connected one minute and completely disconnected the next. If the frame were steel and the weld had failed like it has, I'd suspect that he would have been dragging butt on the rear wheel long ago.

As for the titanium, I'd suspect something else occurred. The frame may have not been welded properly. This could include not properly flooding the area of the weld with inert gas so as to keep from oxidizing the titanium. But that could happen with any weld on any material.