TechCrunch has a great post on hiring for a startup. It's written by Mark Suster, a VC at GRP Partners in Los Angeles. Among the 7 pieces of advice that Mark provides is "Only Hire A Players:"
There's an old saying, "A players beget A players. B players beget C players." Why? Well, A players are discerning and tend to only want to join somewhere where they perceive other A players are. B players tend to have slightly more self-confidence issues so they tend to hire people slightly worse than themselves - thus C teams.
It's good stuff and definitely worth the read.