Even the author's examples of asymmetric, 4-bulge, flat-bottomed cloud icons vary somewhat, though a good case is made that this is a very popular variant. At least one of the example App icons has 5 bulges, and the 'old weather map' example refutes rather than supports the case by being a distinctly different symmetric 3-bulge cloud.
I think the more interesting topic is why asymmetric, flat-bottomed, 4-bulged, 3-radiused, golden-aspect-ratio'ed is so popular in the icon format. Pretty sure it's due to the need to look good bounded in a small square – balanced but not perfectly (unnaturally) so, and simplified to minimal details but not cartoonish.
Right, and of course most (if not all) of those app icons came after Apple announced MobileMe.
Apple released the first iPhone SDK beta on March 6, 2008. [1]
Apple announced MobileMe on June 9, 2008. Both MobileMe and the iPhone App Store launched on the same day, July 11, 2008. [2]
So there was a 3 month period in which some app developer could've independently come up with a cloud themed app icon identical to the one used in MobileMe. I doubt that happened, though.
I think the more interesting topic is why asymmetric, flat-bottomed, 4-bulged, 3-radiused, golden-aspect-ratio'ed is so popular in the icon format. Pretty sure it's due to the need to look good bounded in a small square – balanced but not perfectly (unnaturally) so, and simplified to minimal details but not cartoonish.