The need to trust the person on the other side will always be there (people have always been able to pass on letters and repeat conversations) - but that doesn't change Facebook's role.
"Only put in email what you are prepared to see in the front page of the New York Times"
You may suggest that was an overblown policy, but in 1997, Eric Bradley (who worked about 3' away from me in Building 4 on Middlefield) sent an Email to _a lawyer_ at Netscape - venting about how much "I really do hate that company " when Lawrence Lessig had asked about his application preferences being switched over to IE.
His email (and venting) appeared soon thereafter in the New York Times.
Around here - if you have even the _slightest_ doubt about whether something should appear on the front page of the NYT you either:
o Communicate in person, audibly. o Print it out and hand deliver/email/fax (with the expectation that it will be shredded)
Nobody (except for HR, Finance and legal) keeps paper files anymore, so if you don't want a permanent record - just deliver it on paper and it will disappear. I've been through several discovery procedures, and all that anybody has ever been interested in was email. Nobody even _thought_ to ask for paper files.
Eliminating the for-profit middleman seems like a good first step, this is what Diaspora is all about. Of course not everyone is going to have the technical acumen to host their own node, but there should be a number of node providers to choose from.