Hi, I am a UNIX veteran (>25yrs of using and teaching it) and the number of open files per process has increased a lot and is a tuning parameter.
in the 80s the limit was around 20 file descriptors per process and around 1K - 4K for the whole system.
today both parameters are configurable. ulimit -n shows 256 on my mac lion.
I suggest that Jesse adds either a footnote or some text on how to adjust the number of open files within a process. For example, a high-load multi-threaded single-process server might not have enough open file descriptors available (each connection takes 1).
Just my CHF0.02