That was the secret of Google reader. Being able to subscribe to friends feeds. Social networking based on RSS.
I showed up to the internet party around 2011, a little late for my age, so I was still getting my legs and kind of missed "being there" for a few events, like Megaupload going down and Google Reader getting killed.
I'm honestly starting to get a little stunned at the number of number of times I see people say "yeah, Google Reader could do [this-or-that]".