Where does it come from, then, the idea of privacy? Agre seems to refer to the Industrial Revolution; I'd imagine it was quite connected, for a couple of reasons I can think of: the creation of the industrial work day and the new mass availability of relatively high-tech commodities. I'd guess before that families would sort of huddle together at night by the fire, I don't know, stuff like that.
It seems unhelpful to view the phenomenon of public vs. private as deterministically arising from technology, though. That is the obvious reason, I guess, but that doesn't tell us much about how it works. I don't believe it's just about visibility. Just casting a random line here, but I see something of self-projection (that term probably doesn't mean what I'm using it for though). Ideally, we force certain of our evils into the public sphere--our boredom, our frustration, the things we don't want to do, or rather the things we deny. See for instance the old standby of Tom Sawyer whitewashing his Aunt Polly's fence, with the moral that play is whatever we're not allowed to do, and work is what we are forced to do. The end of the workday comes as the beginning of play and at the same time the entrance into privacy--at that time you can relax, or sleep with your wife, or play with your dog, or watch TV, or (obviously) surf the internet. So even if they're not the same thing, they're connected pretty intensely--that is, privacy and play, or autonomy if you like. The solidification of a system of control around our work and lives doesn't just mean invasion of privacy, it's that the old work/play paradigm is slowly being chipped away at--from both sides, because computer games can now be the same thing as work. When a McDonald's cashier punches a slot or whatever, that action is directly part of the continuum of the control system, but the space in between isn't monitored as intensely. That's a bad example, think about somebody who's not watched as closely instead--an office worker, maybe. The idea would be to approach a kind of autonomy within the system, without being able to break through the system, because the system encompasses everything possible. You don't really have that many more options after work, it just feels that way--if you have an easy job, anyway. As jobs become easier, maybe they stop being work and just become things you do, and as play becomes more demanding, maybe the same thing happens. The question, then, is what are we going to not want to do now? Maybe we'll see a jump in the suicide rate, hmmm?