Do we need multisite with Buddypress or is Buddypress enough for a robust social media site?

Do we need multisite with buddypress? I was only going to use Buddypress, but after reading through your plugins, wordpress and mulitisite notes. The WPMU Dev notes confused me and seems to say that mulitsite is required for a social media site to be effective.

Do we need multisite with Buddypress or is Buddypress enough for a robust social media site or we really need to add the multisite function?