Phil,
Well written and thought provoking. Reading this, I was reminded of a Douglas Adams essay/speech abut Balinese rice farmers and the way their religion is highly suitable to growing rice. The gods that they cite as reasons for this or that aren't necessarily real and some of the practices may actually be useless, but the end product is a very successful harvest. You might ask a rice farmer why he decided to plant this plant here. His answer could involve some custom that if the moon does this and the chickens do that, I need to put a plant here. That's obviously silly, but it doesn't mean the plant shouldn't be there. The customs and beliefs are the basis for how they do things and how they do things is good for growing rice.
I went back and reread the essay and noticed that I remembered it a little wrong. I also noticed that this isn't some interesting overlap between what you and he are thinking about. What you call the memetic immune system he calls an "artificial god". Actually, I think that your concept is a subset of the artificial god. You seem to assume his position of the artificial god and use it to construct this immune system idea. I think that you would enjoy the piece: http://www.biota.org/people/douglasadams/
Phil,
If you are looking for others' thoughts that may be able to tie your post together, you might want to read the Douglas Adams Artificial god that I cite here: http://lesswrong.com/lw/18b/reason_as_memetic_immune_disorder/14az