Here is the user guide for blowing bubbles published by the NYTimes May 8, 2007:

… What used to be a profitable partnership between subprime lenders and Wall Street banks has now degenerated into a cross-country blame game.

Lenders in California say big investment banks encouraged and pushed them to make risky loans. On Wall Street, bank executives say mortgage lenders became sloppy and did not pay enough attention to fraud. Whatever the cause, Ownit provides a vivid example of what went wrong.

William D. Dallas, the founder and chief executive of Ownit, acknowledges loosening lending standards but says he did so reluctantly and under pressure from his investors, particularly Merrill Lynch, which wanted more loans to package into lucrative securities….

In retrospect, it was exactly the wrong time to ease credit: interes rates were rising and home prices were cresting after a sharp four-year rally. Many in the industry also suspected that speculation and fraud were rampant in many hot real estate markets on the coasts and in the Southwest…