Peter Norvig at Google writes about hiring only people who are above the average for your company, a strategy I first heard about from my friend at Amazon.com. Unlike Norvig, I didn't do a simulation to see if it made sense, but it did make intuitive sense to me at the time.
They also talk about the "no hiring manager" concept. NITI used to do this sort of subconsciously, but has been drifting away from it lately (letting individual project managers do their own hiring) with exactly the results that Norvig predicts. I didn't do a graph for that either (and indeed, the graph for that one isn't very convincing; the results are too close), and it also didn't seem intuitively obvious, but having seen it for myself, I agree.
Incidentally, the reason we had for doing the "no hiring manager" thing originally is that I didn't believe that project management skills and interview skills were particularly correlated. For example, I never felt that I was a very good interviewer, so I found people who were good at it and had them do it instead. At the very least, random team members are probably better at interviewing and hiring than project managers - as the people who actually do that kind of work, they know exactly what skills the person will need to have!
Okay, so score two more points for Google, I guess.