Apr 6, 2008 - Margin requirements should be the centerpiece of any congressional testimony dissecting the recent market meltdown on Wall Street (Iceland, Spain, and Poland). The securities acts of '33 and '34 (covered at length in the series 7 exam I took in 1983 when I got my broker's license) contain excellent reforms that cleaned up the excesses that led to the '29 crash. Margin requirements mandating…