Perhaps the most damning report (summarized in these slides (PDF)) on the role of the external auditors comes from the PCAOB's Investor Advisory Group. This is a group of independent advisors that includes Lynn Turner, former Chief Accountant of the SEC, and experts in both internal and external auditors.
I leave it to you to form your own opinion. But, the most interesting facet for me was the divergent views of the AICPA and ICAEW (the external auditors' professional organizations in the US and UK). They saw only innocence.
What do you see?