If you are a teacher of any age, people are watching you--students, parents, coworkers, etc. This includes watching you online.
Like it or not, as soon as you become a teacher you immediately have a responsibility to be a role model for students.
Teachers have been fired for pictures they have posted, comments they have made, and Facebook friends they have had. Don't let yourself be the next one.
So be careful. If you are an educator, consider yourself a public figure. People are interested in everything you do. Some people are interested in catching you doing things you shouldn't be doing.