Pity Merrill Lynch and now-embattled CEO Stan O'Neal: That trend was not their friend.

Instead, on news of Merrill's first red-ink-stained quarter in six years, shares of the top U.S. broker took a beating. As did O'Neal, who conceded that risk-assessment mistakes had been made and that he was accountable for the firm's nearly $8 billion write-down. And O'Neal's week only got worse when reports emerged that he looked unlikely to keep his job amid a furor over unauthorized merger negotiations. Upon that latter development, though, the stock bounced back.

Tough week, Mr. O'Neal.

The outcome was somewhat better for the U.S. equity indexes. On the week, the tech-led Nasdaq Composite (COMP:

Nasdaq Composite Index