Understanding event loops and writing great code for Node.js - Part 1
developer.yahoo.com
developer.yahoo.com
Cooperative multitasking was around for some time but it was eventually abandoned - programmers seemingly don't want the responsibility of cooperating nicely with other tasks.
node.js nicely mitigates the cooperative problem by using events everywhere (allowing queued callbacks to be called). This doesn't mean the problem is non-existent - something more developers need to be aware of.