Fred Wilson has a post about hiring the "best available athlete". I'd like to offer a variation: hiring talented versatile generalists.
I had written about superstars a few weeks ago. Superstars are wonderful, but there's a scarcity problem there. In the absence of superstars, I believe in talented generalists, who also tend to be "natural, all-around athletes", to continue Fred's analogy.
In a start-up, the challenges vary with time. In an organization with defined roles and resposnibilities, you can succeed with specialists, but when you're lean, people will need to pull for each other and play various roles. That's why you need as many generalists as possible.