Digital Identities and their appropriate settings

In the movie Catfish, Angela used a fake identity in order to act as another person. Because she decided to do this over social media, people generally say that what she did was wrong. Interestingly, they argue this as if the act was a reason in itself. I think that the reason people got upset with her is because she chose to be somebody else over social media, where it is expected that people will interact with each other online as themselves. Another reason I believe people get upset about this is that by being deceptive about who you are and building relationships with other people through social media, you could potentially hurt the other person participating in the relationship emotionally. Additionally, people act as though behaving as someone else is universally wrong, but these same people probably wouldn't find a problem with the same behavior if it were to take place during an online game. In an online (or role-playing) game, it is expected that you fulfill the role of another person while you play, and it is understood that a game is taking place, and that what goes on should not be taken seriously, whereas websites like Facebook carry the expectation that you are telling the truth about yourself and what's going on in your life. What it comes down to is that there is a time and place for this kind of behavior. Unfortunately, there are no official guidelines that someone can print off and keep around their computer to tell them, "If you present false information about yourself or who you are on these sites [websites listed here], people will be upset with you and stigmatize you for it in the event that they find out. Here are a list of websites and situations in which it is appropriate to lie about yourself online [websites and situations listed here]."
Of course, I could come up with a list of exceptions that would please me, but I can't come up with a list of exceptions that would please everybody (or the most people). What types of rules do you think should be officialized for conducting yourself online?