Actually, it was structured by pigs

From NC:

In a hearing today before the House Oversight Committee, the credit rating agencies are being portrayed as profit-hungry institutions that would give any deal their blessing for the right price.

Case in point: this instant message exchange between two unidentified Standard & Poor's officials about a mortgage-backed security deal on 4/5/2007:

Official #1: Btw (by the way) that deal is ridiculous.

Official #2: I know right...model def (definitely) does not capture half the risk.

Official #1: We should not be rating it.

Official #2: We rate every deal. It could be structured by cows and we would rate it.