I think part of it may be due to Hasbro cracking down on this sort of thing as I recall one user was told to stop.
I was one of those users. I got a yank down from Hasbro's legal eagles on etsy. All of my plushies, pins, magnets and key chains were removed. I'm not thew only one, I've talked to a few people on DeviantArt who reported similar experiences on Etsy.
In my experience Hasbro or any company really only starts to take notice of you when you're mass producing stuff with their brand on it. Or you're putting your wares on a storefront like etsy or (formerly) shapeways. People like WhiteDove do everything by commission which means the barrier to obtain a plushie from her is much higher than if it were on etsy, and there's also no hard sales data.
I ran into a similar problem a year ago when I was making a battletech tabletop miniature without the consent of the license holders. If I only made 10 or so the powers that be wouldn't have bothered to stop me. however I put it up on a populair battletech forums and in less than a week i had 150 pre-orders with no signs of stopping. and that's when the C&D came. (and a job offer
![Tongue :P](https://mlparena.com/Smileys/default/tongue1.gif)
) Companies have to protect their IP or they risk losing them. And when you put your stuff on a storefront you become an easy target. especially if you become well known because of it.
I know not everyone selling pony stuff on etsy has gotten the C&D but it's much easier for Hasbro find you and go after you. When you're doing private commissions there's no sales data and it's not always obvious that the stuff thats being made is being sold. Also in some countries the person commissioning the product not the artist who is producing the piece is responsible for the rights etc. so thats a bit of a grey area.
Anyway this is just what my experience has been.