My theory on this is to focus first on just the BOBs.
The switches seem to be goofy easter eggs for the most part (tribute room, dance club, race track).
Can we find 2 BOBs on each level? Let's try for that, then try killing them all on regular old legendary. Literally... 'wipe them out'.
The basis of my theory is that the pieces of the vidmaster challenge are just guidelines in the spirit of Bungie traditions to find easter eggs. So, the switches part is a clue that in general there are secret switches to push. The terminal part is a clue that there are secret things to read.
And the bobs: there are secret bobs. By the way, BOB in Marathon stood for "Born On Board" and refered to the colonists aboard the UESC Marathon. Basically, these were any and all humans in the game - in Halo the closest comparison would be the bridge crew in the first level of Halo: CE. Or Marines in general.
So, the point is that in Marathon the BOBs were far from secret, but in Reach, they are these secret golden ranger elites. Just like how the switches and terminals in Marathon were regular old switches and terminals. In Reach they are special and secret (easter eggs, data pads).
It's obvious Bungie wants us to kill the BOBs (wipe them out... 'all of them', and why else would they be called BOBs if you look at the vidmaster challenge as a guideline for secrets - what I'm trying to say is that in Marathon a BOB is just a BOB, but to a vidmaster, a BOB is something that MUST BE KILLED, ALL OF THEM)
Is there a BOB thread somewhere? I say again, 2 per level, let's do it!