Any "reviewer" who gets sent free samples, and who also has an expectation to receive free items from the same company in the future cannot produce unbiased results. This is especially so, the smaller the reviewer's profile.
We all know "reviewers" who have been sent free items that were later accepted to be utter trash, give them very positive reviews.
The very idea of a company sending out free stuff is that you get positive reviews from it. Its a quid pro quo.
Gaming media is full of this. I just have to look at social media timelines or youtube.
Want me to plug your kickstarter constantly on my social media? Sure, just send me a free copy of your 'Movie'- right?
Want a good review of your new console? Sure - just send it to me.
A crappy poorly emulated mini console? no problem. 5 stars.
A podcast that gets sent free game codes just to talk about them for 5 minutes? whats the harm.
We need to know where there is this QPQ relationship. Half of "big" twitter should have "Ad" next to half of their posts.