The nearest historical analogy I can find is the tours of Bedlam, the archetypical insane asylum, where one could take a walking tour, see the inmates, and reassure yourself that you were, in fact, normal. A bit extreme, but any other comparison lacks the friendly, ambivilent disdain that this art form expresses. There are similer emotions and concepts--my favorite will always be the early Christian doctrine of "abominable fancy," the joy taken by the blessed in the eternal suffering of the damned (bring popcorn!), but that lacks the gentle, condescending note, the idea that these are not bad people, not people to be feared--they're not insane or evil, they're just amusingly lame, and aren't we jolly glad we're not them?
Obsession is interesting. No-one can relate to an obsession they don't share. I stare in confusion at my co-worker who can recite numbers from baseball games across the country. I'm sure he'd be deeply worried by the werewolf LARP I used to play in every chance I could. Why is one of these "normal?" (shrug) Not important.
The gentle, ambiable two-facedness of the dorkumentary is what I like most about this neogenre. To simultaneously say "This is good," "These are humans," and "God, what geeks these people be," that is art.