You're being too clever - if you run out of memory, throw away the request and all associated resources and return "500: Internal server error". There are lots of reasons why this isn't perfect (if the OS overcommits memory, like Linux (typically?) does, it will have to kill you to avoid running out; if you need to use swap you're too slow to be useful; etc), but it's not impossible.

node.js (one process for many requests) is a different model than the author is considering; no matter its (dis)advantages, integrating it into the server is not nearly as advantageous as for a process-per-request model (like mod_php).