In a conversation via comments on Karen Schneider's blog , she said that it feels so futile adding reviews to Open WorldCat. Like "droplets in an ocean," she wrote. I agree that we are starting with next to nothing, which is somewhat of an opportunity as well as a challenge. Perhaps an infusion of reviews would help. I notice that Open WorldCat already has a relationship with Amazon; many of the records have links to purchasing titles from Amazon (if you decide not to seek the copy at the nearest library). Perhaps a group of Amazon reviews could be harvested and added to the Open WorldCat records. I see Amazon does have some method of selecting some of the submitted reviews to highlight. Perhaps those "better" reviews could be shared with Open WorldCat as a starter collection.
I also think Open WorldCat has to make the writing of reviews pleasant and satisfying. Writers should get some positive reinforcement, such as being sent thank you emails or having selected reviews posted in a weekly review. Definitely there should be some way of finding reviews by reviewer. There have to be some rewards to market to the prospective review writers.
For more on the idea of reviews and book sales and library marketing, see this post by Rambling Librarian.