There is now a WhatIf.SE proposal over on Area 51. One element that would help it along would be a collection of sample questions. I believe we have that source material already at hand. (They're the very questions we're wrestling with when considering Is Worldbuilding a What If Site?)
I request your help in assembling a list here of questions asked on WB.SE that you think would be good sample questions for WhatIf.SE. Please submit one question per post, and we can bring the highest-voted sample questions over to the proposal.
(I've just grabbed a couple and posted them below, as a way of "seeding" the list. Vote as you think they would be interesting/on-topic on a WhatIf.SE. My working motto for the site is "curiosity: meet expertise.")