post will describe the notion that specifics about social identity and social actions erode as they move away from the origin. So a post that starts out as a specific comment from me to a friend, like this
stoweboyd: hey @gregarious, are you going to SxSW this year?
would be seen just like that to people that are firends of mine and of @gregarious. A friend who only knows @gregarious, and who is following him, might see this:
someone: hey @gregarious, are you going to SxSW this year?
not really about the specifics of messages, but the sharing of aggregated information, like URLs, or topics, and how as you are situated farther away from sources, less specificity is matched by more insight to aggregation. I can see that my third circle is boiling about SxSW.
How does this relate to publicy? We can be more open when a human-scale, living-small attenuation of specifics exists, and everything is not searchable and indexable in-the-large.