Judging by how you've been here for a year, odds are you've never seriously played a Bungie title before. Call it what you will, but this really is something that Bungie does, and it's kind of a game for fans of Bungie.
Also thanks for the bump sir, your contribution is noted :)
While there are instances of other numbers no doubt, it is the number seven that Bungie has an affinity for and are very open about it. Like I said in the previous comment and in the [i]intro paragraph to the topic[/i], Bungie has done this many times before so it's not that farfetched they'd do it again with this game.
Some of these references are a bit exaggerated points of coincidence for sure, others probably are the real deal.
Seriously if you don't believe me at all, [url=http://halo.wikia.com/wiki/List_of_seven_references_in_Halo]here[/url] is a wiki going over [i]some[/i] of the references in Halo. Note there are references featured in books and other media, focus on the games specifically.