I totally agree with the mask idea. We all wear a lot of masks. The mask you wear when meeting with your boss, the mask you wear when meeting with your friends, the mask you wear when meeting with opposite sex (or same sex, for that matter). Some people even wear masks when they are alone.
This mask thing works a lot easier online. You can act like you are totally someone else and everyone will believe you because they don't even see you to begin with. You may be thinking "why people should do that, other than trolls?" Well, I knew a guy in a different forum, where was I a moderator (no big deal, 15 users active). The lies he told us, oh man... I guess he just wanted to be popular and respected. Like a year after he was in the forum, his cousin joined the forum. Strangely enough, his cousin was typing exactly like him, with the same mistakes and stuff like that. Some time later, he told us his cousin died in a gunfight (wtf?). Months after he revealed that his cousin never existed and it was him with two different accounts. We decided to ban him from the forum. After he bombarded us with apologies, we let him back in. Anyway...
Sometimes people love acting like someone they are not. It's most common in online dating services. Though, if you are hoping to get laid with the help of online dating something must be wrong with you already anyway.
And sometimes, people completely throw off their mask when online. They reveal their sexual choices, religious choices, etc only when they are online. They share things they would never share with people they see. They look for advices online without asking for advice from their best friend. I did that too. It's like you throw off your mask but stand on the not visible side of a one-way mirror. You can easily back off from that windows without anyone noticing or caring but you can't do that in real life so you have to be more careful. Also, you can talk to people who you meet in real life more comfortably in the internet. That's a whole another thing.