From the Dean Baker article:

First, while the economy may presently need asset bubbles to maintain full employment (a point I made in Plunder and Blunder: The Rise and Fall of the Bubble Economy), it doesn't follow that we should not be concerned about asset bubbles. The problem with bubbles is that their inflation and inevitable deflation lead to massive redistribution of wealth.

Summers probably would like to use the idea of 'secular stagnation' as a justification for continued bubbles. The problems Baker sees with asset bubbles Summers likely sees as features. (BTW, Plunder and Blunder is a free 186p book in PDF.)

"It is not necessary to have hope in order to persevere."