Professionalism for writers: What NOT to do online

Those of you who are plugged in to the self-publishing world may have already heard about this, but in case you haven't:

A self-published author recently threw a public tantrum in the comments on a book review blog, because she didn't like what the blogger had to say about her book.  He gave it two stars, because although he liked the story, the many grammatical errors throughout the text made it difficult to follow without getting distracted.  He gives a few examples in the comments, and wow, he wasn't kidding.  When you have to ponder a sentence for 30 seconds or a minute before you can figure out what the author meant, you are no longer enjoying the book.

Anyway, the author basically pitched a fit in the comments, insisting that he read the wrong copy of her book, and demanding that he remove the review from his blog.  From there it continued to go downhill, until she was telling other commenters to "F--- off" for criticizing her behavior.

Apparently the entire thing went viral.  It was being linked to on Twitter and Facebook, and in forums such as the Barnes & Noble forums (which is where I heard about it).  The sad thing is that her sales probably did go up a little as a result (bad press is better than no press), but I think for the most part she has alienated more potential readers than she has attracted.

This demonstrates the need for writers to behave professionally at all times, especially authors, and especially on the Internet.  What you type online can come back to haunt you, in your writing career or even in another career.  (A friend of mine found this out a couple of years ago when his employer took offense to some coarsely tongue-in-cheek reviews he had published online.  He now writes anything potentially offensive under a pen name.)

I think this is probably by far the most extreme example of writers behaving unprofessionally online, but have you noticed other authors or freelancers behaving questionably online?