Future historians will long puzzle over how the self-immolation of a Tunisian street vendor, Mohamed Bouazizi, in protest over the confiscation of his fruit stand, managed to trigger popular uprisings across the Arab/Muslim world. We know the big causes — tyranny, rising food prices, youth unemployment and social media. But since being in Egypt, I’ve been putting together my own back-of-the-envelope guess list of what I’d call the “not-so-obvious forces” that fed this mass revolt.