For fashion, afaik "influencers" are indeed using platforms like Instagram much more than Pinterest. That is certainly a situation where they could have defended their turf more effectively.
If I see something on Pinterest I'm interested in, then I'll go to Amazon to see if it's offered there, and if not, I'll head over to Google to see if I can get it cheaper. I'm not going to buy directly from Pinterest unless it's a link directly to Amazon.
