Your on-line identity consists of one or more brands and associated brand-specific identifiers. For instance, to me right now, you're HN!JohnFen. HN, or news.ycombinator.com, is the brand. Right now I'm speaking to you also using HN brand, as HN!TeMPOraL. HN is the brand through which the communication happens. I can't use my Twitter!TeMPOraL_PL account to talk to you, because there's no transport between Twitter and HN. And even if it was, now two brands would be involved in communication.
If you think about it, you'll notice that there's no way you and me can ever talk with one another without a brand intermediary, unless we accidentally meet somewhere physically, or unless some direct connection details could be exchanged through a chain of our physical acquaintances (essentially performing an IP routing over meatspace social network).
If you think about it, you'll notice that there's no way you and me can ever talk with one another without a brand intermediary, unless we accidentally meet somewhere physically, or unless some direct connection details could be exchanged through a chain of our physical acquaintances (essentially performing an IP routing over meatspace social network).