I don't see why they wouldn't want that. Then again since you're running an ethical review site I don't see that happening because they would want to pay and get good reviews.
It's an interesting industry. At some point, we will want to accept advertising dollars from manufacturers (as ad networks are NOT paying the bills), but those ad dollars will not influence the opinion in the reviews. From my understanding of it, there are some manufacturers that are OK with it and others that just want the positive review.