How do you know your unpaired programmers are any more efficient ? I sometimes think the single/pair is comparable to the old fairytale of the rabbit and the tortoise.
Pairing doesn't drift off into days of counter-productive work. I have no idea of how often I've seen developers spending weeks working on stuff that later turns out to be replaced by something far simpler. The single programmer "in the zone" often does stupid things. It's just too easy to produce too much code, when what you want is more punch with less code.
And in posterity, when the dust settles, you find hundreds, if not thousands of lines of code that could have been not written because someone didn't know about library X or technique Y. Pairing improves this problem, but does not remove it. It encourages both individuals and the pair to do more research before diving into mindless code euphoria.
I wish I was able to pair more....
