Many critics have been piling on the Federal Reserve recently, saying its second round of quantitative easing (QE2) will do nothing but spark inflation and asset bubbles. Legendary investment scholar Jeremy Siegel begs to differ.

“The recent surge in long-term Treasury yields has led many to say that the Fed's second round of quantitative easing is a failure,” The University of Pennsylvania professor writes in The Wall Street Journal.

“The critics predict that QE2 may end up hurting rather than helping the economic recovery, as higher rates nip in the bud any rebound in the housing market and dampen capital spending. But the rise in long-term Treasury rates does not signal that the Fed's policy has backfired. It is a sign that the Fed's policy is succeeding.”

What QE2 has done is to “raise expectations of growth and inflation, sending long-term Treasury rates up,” Siegel argues.

“It has also lowered risk aversion, which implies rising long-term rates.”

Bottom line: “Expectations of accelerating economic growth and a reduction in the fear of a double-dip recession are the driving forces behind the rise in rates,” Siegel writes.

Investment icon Warren Buffett is a bit more skeptical.

“We'll see how it plays out,” he told CNBC last month. “I would not want to bet my chips on the fact that the government monetizing $600 billion of debt is going to make a big change.”