In my experience, it's critical to hire a great "anchor team". Thereafter, the hires become a little less critical. The worst work situations I've seen or been involved with had a weak anchor team. There's an expression that "'A' players hire 'A' players and 'B' players hire 'C' players" and that's definitely true in small organizations. For larger organizations and the reason I think the anchor team is so crucial is that an 'A' anchor team can make 'B' players play like 'A-' players and 'C' players play like 'B' players. The infrastructure, thinking and processes put in place by 'A' players can make other less capable players much more comfortable and productive. Make sure your team is supportive of all members and everyone will be better as they play up to the high quality of the other members (when playing sports, I always play better when playing against people who're better than I am).

That said, it's certainly a matter of focusing the anchor team on putting in place excellent practices. Huge problems can still occur if you have a great anchor team but they focus only on solving their own particular problem. You wind up with the best authentication system ever and a broken payment system or with the most incredible sales pipeline ever and technology that doesn't match what was sold.

Clearly, "hire only the best" is impossible for every company and business model. Also, clearly, this discussion is mostly about capability, knowledge, etc; fit with the organization must always be superb.