I'm not sure how much of a chance it would have of succeeding (I'd like it, but would anyone else?). One thing that gives me a bit of hope is the rising popularity recently of email newsletters on specific topics or from specific writers/thought-leaders.
It may, because it doesn't have to build it's own network effect, it can piggyback on emails existing userbase, which is basically everyone.
I was talking with my housemate, we came up with the idea of a combination push and pull following mechanism. I can offer you the option to follow me by sending you a mail with the X-SOCIAL header and a "follow offer" header content, plus a really simple mail body that says "hey, substance just asked you to join their social updates list. it seems you don't have a social client, <click here> to get one". If you've got a social client installed already, the body gets hidden and you get the follow offer in your social client.
However, you could also send me a mail with the X-SOCIAL "follow request" header, and a similar introductory body: "Hey, skewart wants to keep in touch with you via social mail. Download a social client <here> to connect with them". If I have a social client installed, I get a friend request instead.
The great thing is, your email inbox has a timestamped record of all these requests, so it's like a somewhat unreliable replayable social history, which means if I don't have a social client, I can read the introductory body, go grab a social client and come back, and it will re-parse my inbox and offer me the same follow request, no need for you to resend it.
God damn it, now I like this idea.
Man, now I want to build this thing.
My main question is how to support both direct and indirect (via a "social" client (as if email wasn't social)) usage in a sustainable fashion. Otherwise I don't see it gaining traction.