Jesse said "I'm not certain I understand the difference between someone typing something inappropriate on Twitter and someone saying the same thing at an ARMA meeting, or a MER conference, or on a listserv. Public is public is public."

Jesse, IMHO, they are not entirely the same.

If a person stands up and says something at an ARMA meeting or a MER conference can, and the statement turns out to be not what she/he should have said, that person can invoke the concept of plausible deniability: "I didn't really say that", or "I was taken out of context", "I was mis-quoted", etc. 

The reliability of a statement made orally and recorded solely in the memory of those persons present simply doesn't stand the test of total reliability (this assumes, of course, that no audiovisual recording was made of the statement).

With communication media such as email (which includes listservs), Twitter, and the like, there is a record of the statement which has some presumption of trustworthiness, and this record makes it much harder to invoke plausible deniability.

You're still right about the "don't be stupid" rule-of-thumb, in either situation.

Best regards,