You can use a hammer to bang in screws, but it's not usually the best way. If you are using co-operative multi-threading as a way to get Node to handle concurrent CPU-bound requests, you are Doing It Wrong (TM). In general, it's better to create a second (possibly not async) server to handle CPU intensive stuff, or fork stuff off to a subprocess (depending on the actual task). There might also be other ways - I'm not an expert.
I'm sure that if glenjamin had a less trivial CPU-bound task, he/she would handle it a better way (depending on what the task was). But to the Node haters, node-fib is just troll food. It's also an interesting example of how node.js works, but the trolls don't care.
Bunch of people with limited social skills or sanity, in a virtual desert, having flame-wars with strawmen?
Sounds like burning man.