Yes, these types of sites are very common. They are using the reseller api. This is a great way to expand visibility of your portfolio and increase sales. All partner api sales are processed through your Adobe Stock account and commissions are added immediately. Additional information is available here: Fotolia API - Give your users access to millions of RF stock images
Thank you, that answers my initial question, however...
Sites offering to make prints of images use the API to enable their customers to select a nice image and buy a standard license. The license description clearly states that a standard license does not allow them to create and sell products where the image is an important part of the product (such as posters, wallpaper, etc). In my opinion (and from what I understand in the license agreement) the company selling the print needs an extended license! In fact, this would even be the case if the customer supplies an image!
So how does Adobe see this? Why are these companies allowed to work with standard licenses to create printed products? This is very bad for the people that offer their work and unfortunately we do not get a choice to allow this type of sales.
Any customer can purchase a standard license for one time personal use which includes a print for their wall or whatever sort of product they want as long as the product isn't being produced in bulk (or even two) for redistribution the standard license is adequate. If another client wanted the same image for the same product, they would need to purchase another standard license for this to be allowed. The api partner site is essentially displaying the Adobe Stock collection in an effort to increase exposure and drive sales. All licenses are processed through your Adobe Stock account and the commissions are paid as though the sale originated at Adobe Stock or Fotolia.
Thank you again for the answer Mat, I appreciate you taking the time to explain the Adobe point of view on this issue!
Although I see how this construction is good for the print-on-demand business I do not agree and have serious doubts about the legality. The license descriptions provided by Adobe (http://wwwimages.adobe.com/content/dam/acom/en/legal/servicetou/Adobe-Stock-Additional-Ter ms_20160119.pdf ) itself clearly states (3.2.A point 2):
"the primary value of the item of merchandise does not lie with the Work itself. For clarification, producing an unmodified work on a poster is not permitted as the primary value would lie in the work itself"
There is no difference in it being mass-production or not. It is also not the customer needing a license, but the company producing the print! In other words... It is also their responsability to check if work has a copyright if the customer supplies an image. Also, technically the client may be buying a standard license, but I have been looking at these print-on-demand websites and at no point in the process, the client actually receives a license, they just order a print.
I think we (the contributors selling their work here) should be able to expect Adobe to act in our best interest. By facilitating this type business model Adobe helps the print-on-demand business (and themselves maybe), but definately not the contributors.