Excellent post. The one problem I have with the analogy is that pica is almost completely objective; it involves eating non-food items and is (usually) caused by a mineral deficiency. Akrasia isn't quite like that. It's entirely possible that doing Z will cause you to stop doing X, but there does not appear to be an objective sense in which Z is the real thing you need and X was a misguided proxy. Plenty of people play World of Warcraft and never go outside, and they can continue to be excellent, cheerful Warcraft-players. Pica, by contrast, can be harmful itself (ice is one of the most pleasant non-food substances one could pick) and also indicates the body not functioning correctly; mineral deficiencies have both measurable effects on people and (I think) experiential effects in the sense of poor health/energy/whatever mineral deficiencies do. Akrasia seems to lack such objective referents; one could sit down and play WoW for the rest of one's life and, in theory, be perfectly happy about it.