Reviews - albeit usually by fellow authors - appear on almost every cover
And - maybe because they had plenty of experience of the power of reviews pre-web - has adapted pretty well to the on-line power of reviews as well...
Amazon writes to every purchaser inviting a review - it knows for certain that reviews move product (and - as you know - not just in the realm of books)
The lessons? Please, please put aside your own prejudices - if you have any - against reviews and/or reviewers - and engage. Have a look at your own cover (a.k.a home page) and ask "Would our customer opinions - reviews - professionally displayed with independent verification - help drive more business through our website?"
...and Waterstones give them prominence as well
The only sure-fire way to know the answer to that question is to try it out. Become more bookseller - get reviews driving custom through your door.