I don't think it's that easy. My book on Amazon currently has one 5-star review that's just one word and two 5-star reviews with two words each. I am the author and the publisher, and I know for a fact that these reviews are not fake. But they probably come across as fake. I think that there some people who just want to share their opinion of a book without making an effort to write a good review.
Personally, I'd prefer to have only reviews backed up with an explanation. If a book is good, tell me why. If it isn't good, I'd like to know why you think it isn't. That's the only way to make the next edition better.
I have noticed an increase of reviews that typically contain a subject of "<Number> Stars", and either no review body, or a very short review body, such as "good book".
I too hate reviews like that, but I think it's due to Amazon nagging customers to leave reviews for things that are purchased on the Kindle. I am beginning to suspect they have an app or form somewhere where you tap the number of stars and write your review in a text block.
The Kindle prompts to "Rate this book" when you reach the end of an e-book. It doesn't give you the option to enter a review, but only select the number of stars.
Personally, I'd prefer to have only reviews backed up with an explanation. If a book is good, tell me why. If it isn't good, I'd like to know why you think it isn't. That's the only way to make the next edition better.