The notion that bubbles are not all equally bad, and that bubbles fueled primarily by debt tend to be the worst, seems reasonable on the surface, but it's not always so easy to separate bubbles into two camps: those fueled by exuberance and those fueled by debt.
Margin debt, for instance, has increased significantly in China[1] and in the US, stock buybacks financed by debt offerings have been a prominent feature of the current bull market[2].
Central banks have taken so much unprecedented action since 2008 that it requires a lot of faith to rely on analyses of past bubbles to predict what will happen when the current ones burst.
[1] http://www.bloomberg.com/news/articles/2015-04-13/china-walk...