I recently attended a local conference on “Surveillance, Copyright, Privacy: The End of the Open Internet?” (#scpcon). One of the keynotes, @vikram_nz (Vikram Kumar), said that “Privacy is the right to control your own information”. Anonymous email is impossible, he said, because you can’t encrypt the metadata (the header info contains sender details). It is difficult to see why anyone participating in #FutureEd would need anonymity, but I can imagine that whistleblowers, political activists, people who pass info on to journalist, etc. might need to be anonymous at times.
Once something is published online, it is very hard to erase. In any case, it could be argued that, depending on the terms and conditions of a site, something is contributed to a public place online (in as much as any space is REALLY public with so much corporate ownership), an individual no longer has exclusive rights to what has been posted or uploaded. If you say something to someone else on the street, knowing that others will hear you, can you “take that back”?