DISCLAIMER: I'm not an IG blogger nor an Instamum "super-fan" 
. I just wanted to give another perspective to the notion that everything they get is promoted in exchange for freebies & gifts.
It just so happens that Luludumas has bought clothing from my (very!) small business & paid the same as everyone else, without any discount etc. I'm not in a position to offer freebies or discounts and she's never asked for any either. She simply came across my feed on IG, liked what she saw and bought it. From my perspective, she has used her position to genuinely promote a small brand without any incentive to do so. I was absolutely thrilled when she posted a photo on her feed and I received orders and an increased following as a result. That's made a huge difference to someone like me who has zero budget (let alone one specifically for advertising & promotion). I honestly don't think I can be the only one that she has done this for.
Other bloggers with a significantly higher following have contacted me to express interest in an item only to make it clear that it would be a business arrangement - give it to me for free and I'll promote it (not put that bluntly but you get my drift). In most cases, my pieces are made to order. I'm not going to give away an entire working week, plus material costs on the off-chance that someone else might buy an item that the blogger is putting out there. I think it's grabby and certainly goes against the whole "women supporting women" bullshit so lovingly promoted by insta-huns.
Obviously, gifting is rife on IG with many big brands realising that it's cheaper to give away a dozen coats than to run a big ad campaign. I think it's disingenuous to say that we wouldn't happily accept such gifts if they were offered to us in return for slapping a quick photo up on IG.
That said, as a slow-fashion designer, I think this type of promotion feeds the constant pressure to be on to the next "must-have", fast-fashion crap rather than careful consideration of what you buy. Not just that you love it but the conditions under which it was made, quality of fabrics and production (so many of these must-haves are polyester, atrociously made items that I wouldn't buy in a million years), and what happens to it when you sling it to buy the next must-have?