I’ve finally read the full thread (wowww! That was long!). I heard about it through Instagram but I haven’t - and won’t - read the DM article.
The debate is probably over now, it has said everything it needed to (apart from the child sharing issue, which is separate), but I am sort of an Instamum (ugh, that term) so I want to comment. It would have been more relevant, probably, if I’d done so days ago.
I follow two or three of the accounts mentioned here, and know of the rest.
Most of the animosity on the thread seems to be about the grey area of “gifting”. When I first started IG as a business, I gifted. Not to MOD, but to another of the very popular IG’ers who has been mentioned a lot on this thread 
I feel a bit differently about gifting now. Firstly, as a business, it didn’t work so I don’t do it anymore. And secondly, as a consumer, it’s too transparent. Some lives that looked attainable when I first joined instagram are a little more constructed and propped up by freebies than I realised.
But those “freebies" are a reward for being a taste-maker who is willing to share, though. Like a PP, I prefer using Instagram to gain inspiration, rather than magazines. I tend to follow accounts who, even if they didn’t pay for it, probably would as it matches their existing taste (and lots of things popular IG'ers share didn't come for free). As soon as I start to find an account unrelatable, I move onto the next one. That’s how it goes: popular one day, not so much the next.
I follow fashion bloggers who have vaguely my shape, and parenting accounts who share my taste or who I find hilarous (thanks, Mother Pukka
). I love instagram because - thank God I’m not being dictated to by celebrity stylists and 22-year-olds on fashion desks at magazines anymore.
The App has been around for a few years now, and all areas of interest have their own circle of popular accounts, so we’re probably all just starting to lift the curtain up and see how it works.
As someone who owns a business and uses Instagram as its sole marketing, getting IG “right" is much, MUCH harder work than it looks. So those who are able to make it work as a business aren’t just fannying about and snapping the odd iPhone pic and pressing “share”, believe me.
Also bloody love Mumsnet, even though the Instagram mentions of this post are mainly against it. Why?! I mean, the AIBU board aside 
But I say: go for it, Instamums (bleurg, that word!).
(On the secondary, undiscussed subject of sharing images of children: Me and Orla wrote a great blog post about that, which pretty much sums it all up.)