I'm also pretty sure lack of experience also stops you from thinking you could do anything, at least up to a certain level. I think it's combinatorics, really. If you've done N wildly different projects, you have O(N²) possibilities of combining the experiences of 2 of those to produce something novel and good. I have a hard time working with people who are too focused in their domain (e.g. nothing but web apps) because they can't think outside their box.