Telling others to upvote/downvote certain reviews goes against Amazon's Anti-Manipulation Policy for Customer Reviews.
I witnessed an author doing this PUBLICLY on her Page today - not Friends-Locked. So I checked Amazon's policy, and here it is (in this screenshot I took).
If you witness anyone conspiring, and encouraging others, to upvote/downvote certain reviews, please report them to Amazon.
Remember: reviews on retail sites are not for the author, or for the fans. They're for potential readers/customers, to help them figure out whether it's worth them spending time and/or money on a particular product. Don't talk to me about "algorithms", or "if I get so many reviews, I'll get more publicity". STOP IT. Go offline, and write your next manuscript instead - it'll be a much better use of your time.