Wow, lots to think about here.
Zebra, I'm really interested in your point about weaning being very contrived. What you're describing is (if I've got the right end of the stick) a much more gradual, baby-led process. I like that idea a lot.
I agree about the calorie content thing, though surely most people would know that the point isn't about calorie content as such, rather overall nutritional value. I think the WHO guidelines make the point explicitly somewhere about breast milk being nutritionally complete, so other foods would only have a displacing effect. At least that's true for young babies, but that mother of the 9 month old you mention sounds a bit extreme!
That kellymom site is really interesting, thanks SamN! I notice the list of cues for weaning suggests a fairly advanced level of co-ordination, eg sitting without support, pincer grasp, chewing, etc.
Thinking about it, it does make sense to me that if babies can eat a particular food by themselves (reach for it, chew it, swallow it), then they're probably developmentally ready for it (as opposed to having the food pureed and then spooned in by anxious mum reading a timetable from a book). Sort of what Cardigan is suggesting too, I think.
It also seems to make sense that if they are helping themselves, they'll only be taking in tiny amounts at first, and maybe that would give the gut time to adapt and mature. Don't know how you'd prove that though.
OK, going to stop blathering now.....