AIG's weaker position has also placed its credit ratings at risk. Though Moody's, Fitch and S&P affirmed most ratings earlier this month, following AIG's loss and restructuring announcements, they also provided an uncertain outlook for the firm, given its escalating losses, massive restructuring plan and expanded government ownership.

Such an outlook could create big opportunities for competitors to capture business. For instance, some mid- and large-size companies can only buy workers-compensation insurance from "A"-rated carriers -- meaning they must be confident that investment-grade ratings are safe. A recent report from Bank of America equity research highlighted ACE and Chubb as beneficiaries from woes at AIG. Analyst Jay Cohen noted that "a significant number" of ACE's senior executives once worked at AIG and understand its model well enough to "know which businesses to target."

But AIG is aware of the danger and has only redoubled efforts to retain clients. The firm has been touting strength in core areas like property, casualty, life and workers-compensation insurance as uncertainty surrounding its future has shaken existing customers and scared off new business. It is unclear whether AIG is purposefully pushing down prices to retain and expand its customer base, but such a tactic could hurt dozens of competing firms like Allianz ( AZ), AXA ( AXA), MetLife ( MET), Travelers ( TRV), Prudential ( PRU), Chubb ( CB), Hartford Financial Services ( HIG), ACE ( ACE), Aflac ( AFL) and Conseco ( CNO).

AIG's earnings report on March 2 provided some evidence of trouble across several core businesses, though it's unclear whether they stem from pricing or customer flight.

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