At the Institute, a couple of us have been talking about the declining perceived value of anonymity as one of the big impacts of Web 2.0. Social software (however you want to define that slippery term) encourages sociability by giving people stable identities, even if they needn't be identities that track back to a person in the physical world.
I think one of the consequences of the growing centrality of online identity is a growing recognition of how anonymity didn't work online: while there's an argument that it allowed marginal people to be heard in online conversations that they never could have joined in real life, it also served as a cover for– or even promoted– bad behavior, as this t-shirt succinctly put it:
[from Penny Arcade Store]
I was thinking about this recently while driving on the freeway, and having to put up with various drivers doing 80, occasionally passing saner drivers by zipping onto the breakdown lane. One of the reasons this kind of behavior happens on the highway is that if you do something bad on the highways, you can essentially drive away from the consequences of your actions. The odds are incredibly small that you'll be chased down, much less have anyone remember you at a time when they can do something to bring you to account. Contrast this to a small town where everyone recognizes your car, sees you in the coffee shop, and damn well is going to have a word with you if you cut them off on the road.