This sponsorship also often takes place without adequate transparency.
These are the kinds of issues explored in this (pdf) document http://bit.ly/2taOuoL, which includes some examples of publisher sponsorship, and the associated problems of non-transparency that often go with it. In particular, there is a detailed case study of a series of interviews conducted by Library Journal with leading OA advocates that was sponsored by Dove Medical Press.
Amongst those interviewed was the de facto leader of the OA movement Peter Suber. Suber gave three separate interviews to LJ, but not once was he informed when invited that the interviews were sponsored, or that they would be flanked with ads for Dove – even though he made it clear after the first interview that he was not happy to be associated with the publisher in this way.