Typically I only post things I enjoy, but this I posted precisely because I disagree with the premise of the article, or at least the assumption some might make based on the title. Yes, if you say something truly offensive and unprofessional on Facebook (that would warrant firing if said to a parent or school administrator) you can still get fired! The article only points out that ridiculously unprofessional teachers can't hide behind the defense of 'privacy' when information is so easily accessible. A more accurate title for this article? "Friendly Advice for Teachers: Learn how to be Professional with Social Media."
Teachers should 'beware facebook' as much as a surgeon should beware of the scalpel. Yes, it is sharp and deadly, but it can be a precision tool in the hands of an expert. This is no reason to avoid all knives. Maybe 'handle with care' not 'beware.'