Razib, pointing to others' worries about Facebook and privacy, scores an interesting historical analogy:
On the last point, many ancient letter writers behaved as if they were posting on a Facebook wall. Personal correspondence of prominent individuals were written with the expectation that they would be copied and circulated, and sometimes even read aloud. Memoirs and diaries were written in part to burnish reputations, and preserve for posterity one’s recollections.
The early press also got such wide circulation, newspapers carried along with the mail and read aloud to non-literate people. In the 1990's, some internet evangelists proclaimed a new dawn for classic letter-writing, which had been supplanted in large part by the telephone. It took the phone a hundred years to make people give up the fine art of epistolary -- give people a fast, cheap way of disseminating letters, and they'll develop a new golden age of literacy.
What they got were chain e-mails. Then Facebook and blogs.
Which counts, I think.