I'm happy to do product reviews. I don't expect this to happen often, because this website is tailored for photograph and print consumers, not for photographers. Nevertheless, I've recently been asked to do a few product reviews, so I find it necessary to articulate my ethical standard up front.
When I do product reviews I will clearly state if I've been compensated in any way for the review (although I expect that to rarely happen).
For instance, I'm a Nikon user (at least for the moment), because I regard the D810 as the best landscape camera in the world below medium format size and price. I know Sony users will quibble with this characterization, citing the A7R II, and I agree the A7R is a great camera with a sensor about as good as the D810's. But the feature set on the D810 (available lenses, shutter speed, time-lapse, ease of use) for me, still makes the D810 preferred, at least at this moment in time. Similarly, the Nikon D5 is about as good as it gets for low light, wildlife, and sports. I make these statements having paid full price for all my Nikon equipment. In fact, the only time I have ever been compensated by Nikon was for an article that ran in Nikon Asia magazine, and that was done only AFTER I purchased all my equipment (again, at full price).
I have recently been asked to review a couple of products, which as I say, I am happy to do. When these products have been provided to me free of charge for purposes of my review, I will say so. After all, it's only reasonable for a company that wants me to review their product provide it to me at no cost.
But if I remain silent on the matter, you can assume it is a product I purchased for my own use.