I've always heard that when you wash a toy in the dishwasher that you should use no soap, place it on the upper rack, and wash the toy separate from dishes.
1. This seems like a wasteful amount of water to me for just one toy (or even for several). And I don't want to wait until I have enough toys needing thorough cleaning to fill up the entire upper rack. I can just boil my toy in a pot with much less water and in a much quicker time span. The water also gets much, much hotter when boiling it, thus more effectively cleaning the toy, IMO.
2. The hot water heater in our apartment does not get our water very hot AT ALL. So, I would just be washing the toy for an extended period of time with warm water (and, again, no soap).
Thus, I wouldn't feel confident that the toy was cleaned effectively enough. Boiling wins hands down on several counts.