Adding friend activity to members personal activity stream by default

Howdy - you made a rod for your own back WPMUdev by helping me with my last enquiry. Has the internet taught you nothing? Stay quiet, take the help and NEVER HELP BACK! Also, don't google image search for Bea Arthur in case you accidentally see *that* painting of her.

Anyway, I need help, please. How might one add a friend's activity into a member's personal activity stream by default? Basically, I want users to feel comfortable and the easiest way to do that is to replicate other *cough* large social networks *cough* where your default home page is to see yours and all your friends updates. So how do I make that happen?

Thank y'all.

PS please do not google image search for the Bea Arthur painting.