Should bubbles be feared?

I t is likely that the highly expansionary monetary policy being implemented in OECD countries will eventually give rise to asset price bubbles. Should bubbles be feared ? Bubbles have some clearly negative effects: financial crisis if the bubbles burst (but will they burst in the future if monetary policy remains highly expansionary?); taxation of young people who have to buy financial and real estate assets at abnormally high prices. But bubbles may also have some positive effects: Positive wealth effects, which boost demand; As returns on the bubble assets are high, savings are attracted to these assets, which is positive if investment in these assets has to be stimulated. This shows that the nature of the assets in which bubbles form matters greatly: if investment in the bubble asset has no economic efficiency (real estate beyond a certain point, for example), then the bubble is inefficient: it attracts savings to an inefficient use; but if investment in the bubble asset is efficient (for example tech companies), then the fact that there is a bubble may be positive by attracting savings into the right investments.