The Justice Department has been looking into S&P for mortgage-related fraud:
The investigation began before Standard & Poor’s cut the United States’ AAA credit rating this month, but it is likely to add fuel to the political firestorm that has surrounded that action. Lawmakers and some administration officials have since questioned the agency’s secretive process, its credibility and the competence of its analysts, claiming to have found an error in its debt calculations....
The Securities and Exchange Commission has also been investigating possible wrongdoing at S.& P., according to a person interviewed on that matter, and may be looking at the other two major agencies, Moody’s and Fitch Ratings.
With a hedge fund, all it takes is a shred of suspicion to lose your business. Your investors won't wait for you to be charged with anything; they will leave at the rumor of an SEC investigation. With a completely trust-based industry like credit ratings, I'm curious to see how long the clients last.