Most modern sportbikes use aluminum alloy frames. I believe 6061 and 6063 alloys are probably the most common. Ducati uses Chromoly steel tubing, probably at least 4140 alloy, as even thier cheapest bikes are made with top notch materials.
If you're asking about the bikes ability to survive a crash without bending the frame, yeah im sure making it lighter makes it weaker. But still doesn't make it as easy to damage as the rider. All it needs is to be able to survive most minor lowsides to still be a viable trackbike, as thats all any bike can be expected to survive.
are you talking about the "safety feature" where in a crash an automobile implodes/collapses which takes alot more of the force of the wreck and makes the driver feel less impact but yet the automobile is demolished?
like on F1 indy cars, those things are weak (on purpose)