Memory security issues have been the main focus of fuzzing, but it's really useful for other use cases as well, such as: slowness/hangs, assert failures, panics, excessive resource consumption and DOS attacks. We've also done some work with Go to detect race conditions while fuzzing.

You can also do differential fuzzing to compare 2 different implementations that solve the same problem, or fuzz for invariant violations/assertion failures. I think the possibilities extend far beyond just memory safety, and I'm really looking forward to finding other areas in which fuzzing is applicable.