social apps are also not just a an end user application, it's also a massively distributed and open messaging infrastructure. :)

I wouldn't call any social messaging apps that I've seen "massively distributed". "Painfully centralised and proprietary" maybe. I wouldn't use the term infrastructure for them either.

If Facebook disappeared tomorrow, the Internet would continue to function just fine. If email disappeared, we would be royally screwed.

Facebook could disappear for political, legal or financial reasons. Email can't.

regarding facebook, it's just an example, it could easily be twitter, orkut, mixi, etc. what i mentioned in other threads is that there should be a standard created for the new communication method to supersede email. that way vendors could start to produce their own solutions just like email does with ms exchange, lotus notes, gmail, zimbra, sendmail, etc. different clients could also be created: mac mail, gmail, thunderbird, pine, elm, etc.

i agree that facebook is proprietary, but i disagree respectfully that facebook is centralized, they have many datacenters around the world, it's a necessary when you're getting 400M page hits a day and whatever many TB's of photos being uploaded. so do friendster, myspace, orkut, twitter, linkedin, etc.

I was also just using Facebook as an example. The other examples you just provided are the same.

What is wrong with the current group of email standards? And why can't those problems be fixed by extending the existing standards?

Facebook is centralised. It is run by a single profit motivated company. I can't set up a Facebook messaging server. I can set up an email server. Email is distributed because anyone can set up a server.