You're the hiring manager. I'm a professional programmer who works with you. Let's say I personally know and can vouch for the ability of 100 programmers. There are 7 billion people on the planet. What's more likely? That your best candidate will come from my 100-person address book, or that it will be one of the other 6,999,999,900 people in the world you're not looking at?
Now it is likely that someone from my address book will be, on average, a better candidate than a random selection from the rest of the world, but all that shows is that professional references will produce "above average" candidates.
I suppose the difference is whether you want the "best way to find good people," what the parent said, or a "good way to find the best people" which I argue referrals might not be.