Merrill Lynch & Co. (NYSE: MER), at least according to rumors running amok on trading floors, may issue a profit warning and take additional writedowns on its mortgage holdings. MER shares plunged over 5.5% as a result.

I always cringe a bit when I hear of trading floor rumors. Like it or not, traders have a vested interest so it's harder for me to take what they say at face value. Much different than when newspapers report without naming sources. At least there, I'd like to believe, journalistic standards should prevail.

Indeed, while Reuters says that "A Merrill spokeswoman declined to comment on the rumors," CNBC says that sources told it the U.S. broker "is not preparing to issue a profit warning Friday."

With $30 billion worth of writedowns under its belt, it's not difficult to believe that Merrill will indeed require additional writedowns, capital raising, or asset sales. Especially in light of what's been happening the last few weeks. Not only did peers Lehman Brothers (NYSE: LEH) -- down 4% -- and Morgan Stanley (NYSE: MS) -- down 3.5% -- posted weak results this week, but financials in general announced one writedown, or capital raise, one asset sale after another.

Indeed, analysts have been cutting their forecast on financials these days, including Merrill. If a month ago analysts had predicted earnings of 44 cents a share, today the average estimate runs at 16 cents a share.

So-called chatter can have its own agenda among traders so I'm wary of such unsubstantiated rumors. Yet, in this case, its more than likely such a warning would be out sooner or later. Just look at what Citigroup (NYSE: C) -- down 3.6% -- said Thursday.