I believe the management of some social network sites have looked into it and gave it a second thought.
Today, the giant social network site Facebook announced in their blog that they are launching the 'Reply Via Email' feature. This feature was available to some members during the Beta stage (currently closed) and they are going to have it rolled on to all members. So if you have a fb account, and if you have been dying to reply to your status via email (like me), the wait could be over (according to Facebook Blog, see shots below).
The new feature is up and running. From now on, when you receive a new comment in your email inbox, just hit the reply button as you always do with other email message replies, type in what you want to reply to that comment, hit the send button. You are done!
Notice that, the usual "noreply <email@example.com>" has been replaced by a new address that accept replies, for example, I just received a message that when I hit reply I have this "Reply to Comment <firstname.lastname@example.org> "
Thank you Facebook Management!