I'm not sure honest vintage repro sellers, who don't pretend to offer the real thing, are any threat to real vintage sellers. Once you are familiar with the genuine article, there's no way you can be fooled by repros. Or be satisfied by their, erm, quality.
I've got mixed feelings about this, because sometimes I get tired of the labour-intensive care (or expensive dry cleaning) required for most vintage garments and wish for something with authentic vintage style that I can throw into the washing machine and dryer without worrying that I'll ruin it - or it will ruin the rest of my clothes with a dye run or something!
But that will never stop me (as a buyer) seeking out genuine vintage items to wear because most repros really aren't good enough for me anyway (horrible cheap synthetic fabrics, bad cuts/styling, shoddy finishing etc).
I'm going to seriously contradict myself and say that one of my favourite garments is a cream silk blouse in a very 30s style made by a Brighton designer and beautifully finished. It made no claim to being a repro at all, but is clearly inspired by vintage styles. The trouble is, I have to have it dry cleaned by a specialist just like any other vintage item!
What really worries me is poor quality repro being sold on as genuine vintage by inexperienced sellers, or even unscrupulous manufacturers/wholesalers.
Now that IS a problem, and it does have an impact on the genuine vintage market by disappointing buyers who thought they were buying the real thing.
Sarah