Andrew Ross Sorkin’s DealBook column in today’s NYTimes offers up a fascinating and downright scary take about an online vendetta against a Wall Street banker that apparently led to his resignation from Credit Suisse.

The banker, Steven Rattner (not the developer, however), recently left the investment bank, according to the article, after an extra-marital affair five years ago with a married woman. But what’s interesting is how, years after it ended, the woman’s husband decided he wanted to hurt some more.

As Sorkin writes, It is a cautionary tale about the fragility of reputation on Wall Street and elsewhere: **

Kelly Cosgrove, the woman with whom Mr. Rattner had an affair, was married at the time to an Australian named Tommii Cosgrove. And after he learned of the affair, Mr. Cosgrove decided to make it his life’s mission to damage Mr. Rattner. And with Mr. Rattner’s resignation, he may have succeeded.

Mr. Rattner, who is apologetic and contrite, did not commit a crime. He did not violate Credit Suisse’s code of ethics. His affair was not with a subordinate or a peer — Ms. Cosgrove had no relationship with Credit Suisse.

He added, “I love my wife and my kids more than life itself.” But he also said he was willing to be interviewed for this column because it offered a cautionary lesson. Once Mr. Cosgrove pushed his allegations to the Internet, Mr. Rattner said, there was nothing he could do to stop it. “It’s just amazing to me,” he said, describing Mr. Cosgrove’s persistence as “viral.” “And there is no way to fight back.” ** Well, there is a way to fight back online, which is to make sure you’re side of it is being heard and to get your story out there too.

The case reminded me (in a small way) of a disgruntled source who insisted I change a story I wrote about AOL’s e-mail relaying policy. The policy was changed as a way to combat spammers on the ISP’s network, but it was penalizing plenty others who don’t spam.

I saw a post on Slashdot from a legitimate user who was being penalized by the policy. I reached out to him for comment and quoted him as one who had been wrongly penalized. But he felt I had mis-portrayed him and proceeded to launch tirade after tirade asking for changes on the story. I was happy to follow up, I wrote back to him, but I didn’t where or how in the story I made him look like a spammer. The story was how people like him who are legit users were being penalized. I suggested a follow up with him to help clarify. On it went.

Then it got nasty. One link he sent to further “discuss” contained malicious code. Right there, I ended the discussion of any follow up, clarifications or changes. He later created a wiki page that tried to damage my reputation as a journalist. (And deleted my comments that discussed the issue; so much for fair play).

The Rattner case in the NYTimes article is serious business, involving his family, his job and his reputation in his community. We see this all the time on the Web but this case really drives the point home. At least, by way of this article, the tactics of the person who conducted the vendetta are also being exposed.