I posted earlier about the ethics opinion from the Massachusetts Bar that caused a stir about making an attorney's email publicly available without some disclaimers.
To follow-up there is an article in this month's ABA Journal on the topic: The Too Much Information Age: Authorities seek clarity on unsolicited information from prospective clients.
It highlights some of the worst-case scenarios of why law firms should be putting disclaimers on their websites. A "California lawyer received an e-mail from a woman seeking a divorce lawyer—who revealed information about her secret extramarital affair. . . . The [California State Bar's Ethics] committee noted that a disclaimer stating, “I understand and agree that law firm will have no duty to keep confidential the information I am now transmitting to law firm,” would have eliminated any reasonable expectation of confidentiality, allowing the lawyer to represent the husband in spite of the wife’s admissions of adultery."