You should read their methodology. For one, they are entirely subscriber supported. Secondly, they send out people to buy the product at random stores off the shelf, not solicit manufacturers to send possibly biased batches. Thirdly, manufacturers often write in to them when they receive bad reviews, urging a retest. (The back and forth of those letters gets published.)

Sure, it could all be a hoax. But we don't have too many alternatives.