Berkshire-Hathaway faces downgrade; AAA rating endangered

Uber-investor Warren Buffett's Berkshire Hathaway (BRK.A) is in danger of losing its credit rating from Standard & Poor's, the credit rating firm said Tuesday, citing concerns that losses on equity investments are sapping the company's strength. Fitch Ratings, another big bond rater, already went a step further, downgrading Berkshire earlier this month, in part over similar worries.

If it seems like AAA-rated companies are becoming an endangered species, it's because they are. Generally speaking, big financial concerns like Berkshire don't warrant top credit ratings in such a volatile market, according to Fitch. And after downgrading General Electric (GE) earlier this month, S&P now bestows its top rating on the debt of just five industrial companies, and at least one of them is in danger of going the way of GE.