I would say a definite yes, reviews can lead to sales, which lead to word of mouth--sometime a great book catches fire. Small press and indie POD authors don't have much in the way of promo or marketing opportunities, and solid reviews from large popular sites do carry some weight as far as readership and exposure. Talking about the legit, free ones, of course, who ask nothing more than a PDF copy of an ebook or, an arc, or a publisher-donated print version. I had a few reviews result in a couple dozen sales. Problem is, you have to keep slinging that book out there, keeping your name and book title in constant circulation.
I must belong to over 30 display and reader's sites. I contribute articles, blog, and try to interact. It is massively time consuming and the results from these efforts are very poor to non-existent, as far as sales go. Why do I do it then? Ain't got no other choice in the matter. Keeps my Amazon rank down by those one-sey and two-sey sales, if that says anything.
Tri