E-mail, the Internet's first killer app, can injure companies and individuals when not used with care.

In its attempt to document the risks of electronic messaging and to make the case for the value of its services, Proofpoint, an e-mail security company, has assembled a list of what it considers are the "Top 10 Terrifying E-mail Blunders of 2009."

Keith Crosley, director of market development at Proofpoint, says the incidents his company has cited demonstrate the ongoing need for user training, for corporate e-mail policies, and for technology to enforce corporate policies. He says that only about a third of enterprises have deployed systems that can identify and block the unauthorized transmission of health or financial data.

The incidents that follow are, according to Proofpoint, in no particular order.

E-mail That Empties Bank Accounts: In September, the URLZone Trojan was reported to be spreading through e-mail and compromised Web sites, and emptying victims' bank accounts. It's even sophisticated enough to create forged balance reports to conceal its looting.

"No More Internet Banking For You!": That's what FBI director Robert Mueller's wife told him after the agency head clicked on a phishing message and nearly surrendered his personal information to a phishing Web site.

White House Spam: A White House effort to set the record straight about its healthcare plans in August led to the sending of unsolicited e-mail. The incident wasn't exactly a disaster. But it was it great public relations either.

Hotmail Accounts Blocked: Earlier this month, Microsoft blocked tens of thousands of Hotmail accounts that the company believed had been compromised as a result of a phishing scam. A security researcher at ScanSafe subsequently argued that exposed account credentials were gathered using a data theft trojan rather than a phishing attack.

Department Of Gaffes: Social media start-up RockYou reportedly managed to mess up its e-mail messaging three times in the past year. In January, it sent a mailing list message using the CC address field rather than BCC, exposing the e-mail addresses of everyone on the list. In November, it reportedly asked contractors for W-8/W-9 information in a message sent to a mailing list, which prompted replies containing personal information to the e-mail list rather than to the company's accounting department. And in September 2008, RockYou reportedly revealed over 200 e-mail addresses in a message it sent out.