What is a Housing Bubble; and is another one forming?

With economic unrest in Greece -as well as other parts of Europe- there has been no shortage of talk about whether or not the U.S. could be facing another financial crisis. Others look to the rising values in the housing market, and speculate on if we are already in the middle of another housing bubble.

From Keeping Current Matters:

What actually is a price bubble?

Here is the definition according to Jack M. Guttentag, Professor of Finance Emeritus at the Wharton School of the University of Pennsylvania:

?A price bubble is a rise in price based on the expectation that the price will rise. Sooner or later something happens to erode confidence in continued price increases, at which point the bubble bursts and prices drop. What makes it a price bubble is that the cause of the price increase is an expectation that the price will increase, which sooner or later must reverse itself.?

Does Professor Guttentag believe we are in another housing bubble?

In a recent article, he explained:

?My view is that we are a long way from another house price bubble. Home buyers, lenders, investors and regulators now understand that a nationwide decline in house prices is possible — because we recently lived through one.?