The mistakes are harmful. When you mess up your string handling in Perl or Python, you end up with double-encoded utf8, or something. When you mess up your string handling in C, other people on the Internet get a shell on your computer.

C is serious business.

(Incidentally, I've written event-driven programs with libev in both C and Perl. My load is usually so low that doing it all in Perl does not affect the number of requests I can handle, nor does it impact latency. The IO is the bottleneck; the article even says it only uses 2% CPU. Why risk insecurity when you don't know C and it doesn't even improve throughput?)