At first I misread what you said as "NodeJS can easily make use of multiple cores with child processes, by design". It's true, though. Many NodeJS proponents know this. Google Chrome, which uses the same JavaScript engine, V8, works the same way. The fact that it uses lots of lightweight processes is a big selling point of Chrome.

I'm not completely sure about this, but I remember hearing that SpiderMonkey is more suited to using threads, and that's why CouchDB uses it rather than V8.