RSS to compete with social networks

What we are missing in RSS is the ability to send content privately. For instance if I want to mark a blog entry to only be viewable to certain people I really can't do that while also syndicating it. Someone would have to come to my website, login and view it. This puts RSS at at a disadvantage compared to social networks that have privacy walls in place where members can view restricted content from other members on their friends list.   

It would be nice if RSS supported some kind of protocol for doing this. So that I can mark a blog entry as readable to only certain email addresses. Then people can put their email address in their RSS reader and if the entry comes through with their email address on the include list, it will show them the restricted content. 

I'm not entirely sure how this would work. The reader would have to ping back the source the original feed came from and request a hidden feed that contained the information that was left out of the public feed. Which means the software that publishes would have to generate special hidden feeds for each email address on the include list for that entry. 

Ultimately the end user experience should feel similar to circles on google+. A person can submit their email address to your self hosted weblog and you can then manage all those people by putting them into groups. Whenever you add a blog entry or image or video or audio clip you can mark that content to be viewable to only certain groups if you don't want it public. 

Similarly it would be nice if RSS featured some kind of profile feed. Where instead of entering email addresses (like mentioned above) someone could just sumbit their profile URL and the the reader would parse the RSS profile feed from it. It would send basic information like username, first and last name, profile photo, website URLs, description, interests, gender, relationship status, who I want to meet, etc. This information doesn't necessarily get saved to the website it's submitted it, but instead it gets pulled up every time that person appears on that website. 

The idea is that a social network could be created using personal websites without a central repository. A person submits their profile URL from their personal website to other personal websites. They are then added as a contact that can be grouped and view restricted content coming form that site in their chosen feed reader.