According to Do Blogs Influence Purchasing Decisions? at Christian Marketing, blogs do, indeed, influence buyers. "A recent Technorati study (Technorati’s 2013 Digital Influence Report) found that blogs hold a lot of influential power on purchasing decisions of consumers." "...when bloggers like your book, this influences people to buy it."
I found this incredibly interesting because among bloggers I know there have been questions about whether or not we're just writing for each other. How many books can we read/buy? I've also heard some reservations from writers who've done blog tours as to whether or not they were worth doing.
Perhaps Christian bloggers influence purchasing decisions and others not so much?