Actually it does. Read your TOS for pinterest and instagram
"You grant Pinterest and its users a non-exclusive, royalty-free, transferable, sublicensable, worldwide license to use, store, display, reproduce, re-pin, modify, create derivative works, perform, and distribute your User Content on Pinterest solely for the purposes of operating, developing, providing, and using the Pinterest Products."
If they have a license to use it, they have rights to give others the right to use it. That is how things get re-pinned.
The cow is out of the barn on this.
But what probably happening is this; There are bunch of really small time players on Amazon who actually don't have any stock. They take stuff off ebay, etsy etc, and post it on Amazon. When they get an order they order it. Since they don't have the item and they need a pic they take the seller's one.
