The really big change here is that we've got a medium which scales from small groups – me talking to a group of my friends – all the way to "now I am making a public declaration." And because previously, we had a world where, if somebody said "I love you" on the phone, you knew it was meant for you. And if somebody said "I love you" on the TV, you knew it was specifically not meant for you, because the mode of carriage lets us figure out how that message should be interpreted.
And that's now broken. There are people having relatively personal conversations with their friends, yet they're doing it in a public medium. But that's no different from sitting around talking with friends in the food court at the mall. If you want to go down and find a group of teenagers chatting to each other at the mall, you can sit at the next table over and listen in, but then it's pretty clear in that situation that you're the weird one.
What we don't yet have is a set of social norms for figuring out – in a medium like the web, which scales from intimate personal address all the way to full publication – which messages we should be paying attention to and which messages we should be ignoring.
