Use Friends as a criteria to manage blog visibility?

Hi:
I have configured a site which is by-default private blogs. It occurs to me that a "friend" relationship may a community appropriate method to "permit" collateral blog visibility.
Questions:

  • Is this, by chance, a default behavior?
  • If not, is it an option?
  • If not, where might I find list-friends code? Found It -- But it sure looks like this is already built-in to BuddyPress
  • Are there docs about this?

Thanks in advance...
squibm