Remember when you got started on Facebook? There was that phase a few months into it where every high-school friend was suddenly back on your radar, whether or not there as any reason to have remembered them in the first place. Waves of old and new faces would wash up on the shore of your in-box. Some of us indiscriminately accepted all. Some others took more time to approve or maybe ignore some of the more hinky ones.
Social Networks right now are merely dumps of nearly infinite connections, powered by XML and RSS. If the robot even thinks there’s a connection, it is programmed to go ahead and make it, hoping that you, the human, will sort it out later.