There are no jokes when it comes to a video game's release. The truth is that there is a large plot behind this event full of spoilers, since Bungie has always mentioned to the people that want to avoid spoilers to "go dark"
Probably that was a simple plot to distribute the game earlier and cause a small fuss causing the game to be discussed and to be highlighted for a little while before its release.
It's clear that a large plot is behind this, which we will never know who started this plot and which were the people behind this. Plus, there is no way that justice can be applied, I would not wonder that Microsoft employs themselves distributed the game to the various "xbox hacking" communities.
The only reason was to motivate the various children (yes, children is appropriate) To go around and advertise the game everywhere.