2) The speed and efficiency of backtrace generation can affect recovery times. It's far more than 50ms for a lot of server-side or embedded applications.
3) Large programs today cannot be debugged feasibly (as in, good luck in generating a detailed crash report, your system will likely not have the resources), especially if they're time sensitive as well (tracing is the typical approach there). There are engineers out there who have to spend hours just to extract a small memory dump from a single thread.
4) Certain classes of bugs are best observed over time and minimizing jitter is important (more on that later as we unveil some features of the advanced tracer and user interface).
Less intrusive real-time profiling is interesting to us, but currently only in the context of state leading to a fatal bug (this also includes bugs that involve hanging such as an infinite loop). The technology does have applications for performance management but this isn't something we are focusing on at the moment.