To be honest, Krugman does not advocate bubbles -Summers doesn't directly do so either, although it would be quite a natural conclusion from some of the things he said. He mentions that Summers spoke of secular stagnation and finishes with "I fear he is right".

Expansion of public services would be good, although I would like to reverse inequality directly first. But we can't just expand because of the physical constraints (and even from the fact that there is only so much we can meaningfully consume) -so we'll have to restrict individual production to maintain full employment.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi