With so many business scandals lately, there’s often a damning e-mail exposing wrongdoing, often sent by high-level employees.

Just last week, government officials investigating the collapse of MF Global released an email from the firm’s assistant treasurer that could implicate the CEO, former New Jersey Governor Jon Corzine.

The e-mail states: “Per JC’s direct instructions” millions of dollars were transferred out of customer accounts to cover a shortfall at the defunct brokerage, an act that could spell legal problems for both Corzine and the treasurer.

E-mail evidence like this isn’t unusual. Last year, an investigation into phone-hacking charges at News Corp. unearthed damning e-mails that showed top managers were informed about widespread illegal activity. And even the Oracle-Google patent fight has a “damaging e-mail” that is part of the saga. According to a recent article in Computer World, Google has been trying to keep an e-mail written by one of its engineers out of the case.

So, the question is, why do people keep putting potentially harmful information in e-mails? Sure, it’s great for prosecutors who want to expose malfeasance at companies, but after so many public e-mail faux pas you’d think people would have wised up.

One of the top reasons they haven’t is “hubris,” maintained Dave Scher, an employment attorney with the Employment Law Group. “People think they’re above the law.”

Scher represents employees in cases of retaliation or discrimination at work, and with about half of his cases he’s able to find e-mails that corroborate or confirm retaliatory or discriminatory conduct.

One of the most blatant e-mails came from a boss who was pretending to be a licensed therapist. When his employees exposed him, the manager sent the worker an e-mail basically stating he was firing him because he revealed his lie. It was a retaliatory move that’s illegal under labor laws.

Indeed, about a quarter of companies have had an employee e-mail subpoenaed as part of a lawsuit or regulatory investigation; and 9 percent ended up in court because of an employee e-mail, according to the most recent report on business communications policies by the American Management Association and The ePolicy Institute. This is despite that about 80 percent of organizations have written e-mail policies, the study found.

Stephanie Weiland Knarr, a licensed psychotherapist from Laurel, Md., isn’t surprised that people who engage in shady acts have no qualms about letting it all hang out on e-mail. “The personality type of someone who is engaging in illegal behavior is often narcissistic,” she explained, adding that they think they’re invisible and above the law. “These types of people like to take risks and even if they’re caught and the writing is on the wall, so to speak, they still deny it.”

What may also be driving some of this is that many employees just don’t take e-mail seriously, surmised Nigel Cannings, technical director for Chase Information Technology Services, a London-based firm that does corporate compliance.

“What we have found is that people just don't think of e-mail as ‘real,’” he explained. “To them it's an ephemeral thing that is sent off into the ether, and which is a) private, and which b) can be deleted. Usually, both are untrue.”

Indeed, in most cases you can’t just scrub your e-mails away if you realize they could be career killers, or land you in legal hot water.

“Depending on industry and the size of an organization, e-mails are immediately written to an enterprise repository, which is accessible by legal and compliance functions. And which cannot be deleted, even if they are deleted from the e-mail client,” Canning noted.

And, he added, “Financial regulators insist that e-mails are maintained for potential later investigation. Increasingly this is the case for IM messages as well, and they are likely to be the next big area where people get caught out.”

It’s not just illegal deeds that are exposed via e-mail. Patti Johnson, a career expert and the CEO of PeopleResults, said the e-mail flubs she sees most include:

• The misinterpretation: “E-mails are often misinterpreted because you wrote it quickly, used the wrong tone or copied the world. A poorly worded or quickly written e-mail can send the relationship in a downward spiral because it is misinterpreted.”
• The misused CC: "This is often the equivalent of saying I need to let your boss know because I'm not sure you will get it done, or I need someone else to be involved. Use the CC with intent or you can end up with a trust issue on your hands unintentionally.”
• The address mixup: “E-mails sent to the wrong person. Yes, it happens and it isn't pretty. You type the person's name in you are complaining about.”
• The angry: “E-mails sent when you're mad. This is time to take a deep breath and make sure you have the facts and pause. A good rule of thumb is if you are going to send a flaming e-mail out, sleep on it first or at least walk around the block. Because once it goes - you can't get it back.”

In the end, e-mails are “permanent and very, very mobile,” stressed Margaret King, director of a consumer research think tank, The Center for Cultural Studies & Analysis.

“Never put anything in an e-mail that you would not want quoted in the New York Times,” she advised. “If the material is that sensitive, ask the recipient to give you a call, and transmit that way.”