Okay some things I can discern:

1) Topical is good, especially if the media goes crazy over the issue (swine flu, Obama dogs)
2) Anachronisms
3) Anthropomorphism
4) Sex, TV, Music, Relationships = good
5) 20-30something angst = good

Oh god they're just so all over the place. Maybe the best thing to do is to draw up one every week, start submitting and keep at it until they're like "why don't we let this one through, maybe the chap will stop."

Excellent question. I haven't read these in years. I think I stopped because they all started to soud the same, so I understand your search for a formula.

A sprinkling of them have titles that when you click the list, the list is a joke on the title itself, and most of them it just seems like if you come up with a good title, you're halfway home.

My only idea so far is riffing on slumdog millionaire, called "Other British-helmed Indian Extravaganzas", which jokingly lists the bloodbaths etc. involved in their colonial rule here. But they'd be obscure references for McSweeneys readers plus it's hard to come up with 6-10 clever names for the incidents.

Actually I think the answer to the McSweeney's problem and the Vanity Fair problem are the same: Suck off the editor!! (That leaves the Beckinsale problem)

It seems like there are a couple categories:

what if older cultures had our technology?

Puns (where the punchline is usually the title itself or the last entry - cf. "distressed denim")

Double-meanings

Things I would have Kate Beckinsale Agree to in a Pre-Nuptual Agreement?

I published a few lists with McSweeney's several years ago, and had twice as many rejected, so I can tell you this: I don't think there is a formula. I think they use some variation on the old "stairs" method of grading papers, in which they fling printouts at a staircase and pick the ones that land the highest.

Do you have the rejects filed away somewhere, scody?