I learned how to recognize bubbles from the book "Trend Watching" by Ron Insana. He wrote:
**** Begin Book Excerpt ****
Four ingredients occur at the beginning and during the inflating of all bubbles. When the first three exist simultaneously, a bubble will inevitably emerge.
1) Eureka!! New discovery or invention (e.g., the internet or fancy new derivative securities)
2) Easy money: Low cost or highly available credit - the most necessary pre-condition for a bubble
3) Government Largesse: Subsidies, tax incentives or special treatment for particular industries
4) Auspicious economic conditions
One key ingredient in a bubble is some form of mass participation. Bubbles of epic proportions have always involved entire populations who were consumed by the desire to become wealthy without working.
Endings to bubbles do not come without warning. Big bubbles are always marked by an obvious deterioration in the positive factors that inflated them. Tight money or higher interest rates burst bubbles.
**** End Book Excerpt ****
Now, bearing in mind what he wrote, let's look at the economy.
The collapse of the housing bubble and the recent collapse of the stock market have wiped out the wealth of most of the population. They can't participate in bubbles right now. Therefore future bubbles will be smaller (the recent commodities bubble is an example of a smaller bubble). The current stock market bubble is inflated by government purchases of "toxic assets". Those purchases will eventually end and, several months after that, the bubble will pop.
While credit is scarce for small and medium businesses, there's plenty of money for big business.
Federal Reserve purchases of toxic assets give banks lots of money to speculate in commodities and securities (including the stock market).
Auto companies got some special treatment recently - though not enough to make much of difference yet.
There has been talk of subsidizing "green" industries that reduce CO2 generation, and for subsidizing infrastructure building and repair.
The next "Eureka!!!" will probably come from biotech, but that's probably a decade away.