hiring is really simple: you can straightforwardly filter out the obvious no's, but beyond that, it's a crapshoot. basketball analogy time! (my favorite =) the NBA employs 450 of the best basketball players on the planet, and at any given time, the league is evaluating a few thousand more (out of hundreds of millions of basketball players, out of ~7.5 billion people worldwide). all the easy filtering is done. every y…
Fortunately, for smaller companies there's another option - use personal networks to find candidates, the chances would be much better. For googles, they can just afford some misses, it costs but not something they couldn't stomach.
going back to basketball, no team has yet to sign 10x nba all-star carmelo anthony this year, and 8x all-star dwight howard only just signed with the lakers (on an unguaranteed minimum contract) because of a season-ending injury to demarcus cousins. both players are individually very talented, but are reputed to be hard to play with (thus lowering team productivity & efficiency).