Early on, when software was developed by computer scientists, just people working with computers, people passed around software because that was how you got computers to do things.
Tim O'ReillyThe nice thing about twitter is the architecture of visibility. Email is invisible unless you reach out to someone directly. With Twitter, anyone can follow you and this is one of the big changes that was really introduced by Flickr, was this wonderful idea that you can follow somebody without their permission. Recognizing that relationships are asymmetrical, unlike facebook where we have to acknowledge each other otherwise we canโt see each other.
Tim O'Reilly