Also a segfault IS the protection layer intervening, it is equivalent to a exception in other languages. The real problem is, when there is no segfault.
This is absolutely true. But even this does not happen in the software I use every day. Software written is C is definitely the most stable I use - by far. That there are people running around claiming that it is impossible to write stable software in C and it crashes all the time due to bugs is rather unfortunate, as it is far from the truth.