George M. Cohen, Of Coerced Waiver, Government Leverage, and Corporate Loyalty: The Holder, Thompson, and McNulty Memos and Their Critics, 93 Va. L. Rev. In Brief 137 (2007), html, pdf, examines the flap about the McNulty Memo (and its predecessors) and concludes that the "coercion" involved in requiring corporations to waive privilege in order to be seen as "cooperating" with an investigation is just not a big deal.
Cohen's concluding paragraph:
The vehemence of corporate opposition to the government’s waiver policy may be a matter of whose ox is being gored. It is one thing when the corporation on its own wants to finger some low-level employee and label him a “bad egg” acting contrary to company policy so that the corporation can avoid prosecution. It is quite another when internal investigations turn up evidence of misbehavior at the highest levels and diffused throughout the organization. But that is what the recent corporate scandals are all about. The “coercion” that corporations claim to suffer may in fact be the discomfort that upper-level executives feel when they have to choose between waiving the privilege for the good of the company and saving their own necks. If so, then criticism that has been dressed up as a noble stand in defending a venerable privilege against government abuse is in reality just the corporate bar’s age-old attempt to protect upper-level corporate management rather than the entity client that corporate lawyers are supposed to serve. That would not be a surprise. The surprise is that people have been taken in for so long.