I thought it was amusing that he went on to say "Much of Fog Creek uses the Microsoft Stack. I can’t even spell ASP.NET and they’d still hire me." - Joel Spolsky wrote a great article on the value of knowing a language in depth: http://www.joelonsoftware.com/articles/LordPalmerston.html

That said, his point is still largely true - you don't need your entire team to be specialists. But don't underestimate the value of knowing <some significant technology> inside out, backwards, and upside down.