It comes from proof of share, and when you share your posts on twitter you can tag posh and then share the link of your tweet in here. From what I know it was initiated by and they used to curate posts tagged with posh. It's easier to find them when tagged so. I also see it as encouraging others to share more hive posts on twitter so the world would hear about us.
RE: If becoming mandatory to further live "free" in this society, would you accept a RFID chip under your skin?