Distributed systems are nothing new (AST's Amoeba goes through some of the mapreduce contortions), but there are very few programmers comfortable thinking that

Distributed systems are nothing new (AST's Amoeba goes through some of the mapreduce contortions), but there are very few programmers comfortable thinking that way- you may recall, even SONY had an awful lot of trouble recruiting talent. It's in Google's best interest to increase the market size of "parallel programmers"- to actually be able to pick from more programmers who can "think" in mapreduce, improves their hiring options. I doubt this fact escaped Google: mapreduce stands on shoulders of its own giants who faced this problem as well.