It's no secret that collaboration helps in the formation of good ideas, but this charming little video from writer Steven Johnson explains why it works.
The concept is that you have a partial idea, or a hunch, that needs to be combined with another hunch to form a fully developed, great idea. Sometimes patience and thought will get you there just fine, allowing the fragments of ideas time to incubate, but generally, your great idea will occur thanks to the combination of your hunch with someone else's hunch. To get to that point, you need to place yourself in environments that foster good collaboration. Johnson argues that while the web can often be a distraction, it can also be a fantastic collaborative environment for the development of great ideas. You next idea may be formed best by finding an online community that'll give you good, positive feedback. I can't help but think of Quirky as an example of this concept at work.
But if you're reading this, you really ought to be watching the video. It's a far more entertaining explanation of where great ideas come from.