I think it is obvious that when people can hide their identity, they will do things they normally would not do. Often times I find myself doing embarrassing actions in public, but not really caring because nobody knows who I am. Conversely, had I been in a room with people who are always with me, then I probably would feel more embarrassed.
This distinction is obvious. When we are worried about our reputation and "ruining our names" then we are extra aware of the people who around us who may know us. If we are convinced that people don't know us, then we feel comfortable doing things we normally wouldn't do.
However, I think there is more to this than just inconsequential things. For example, one of the interesting things about Youtube is that the people who comment do so anonymously. They can say whatever they want no matter how prejudice or hateful. Since there are no consequences to their actions, they can be outright rude to others without having to worry about ruining their own reputation. (Compare to Facebook where the people who right on your wall are identifiable and therefore accountable)
I think also, this could be applied to crime in general and to more broader social settings. Think about the New York subway for a moment. Plenty people graffiti and trash the subway system. However what if people were identinfied as having been on a certain car at a certain time. Each person could hold a radio emitting ID card that could identify them. Then each car can scan for the IDs and people will be linked to the cars that they are on. In other words, you can only ride the subway if you identify who you are. And once you do that, then you are less likely to commit a crime. (The problem would be if someone lost their Id card...but then they should cancel it ASAP like a credit card)
If people are identified in real life (and online) then I am convinced that a lot of the information on the internet would be more trustworthy and the slander will be limited - because people will only want to communicate with people who they can trust and with people who do not need to hide behind anonymous personalities. Also, crime will be less because people then would be identifiable.
Setback? Big Brother is watching...