Dear authors. The best promotion you can have are reviews. Lots of them! As different as possible, good ones, bad ones, crazy ones.
Especially as self publishing authors getting these precious pieces of advertising is hard, and of course everyone asks their friends, and blogs that they like and follow... often enough it's through a review request that authors and reviewers become friends, and that is a HUGE problem.
Since Amazon has battled with fake reviews, they have put a strict set of rules on who is allowed to review for whom. And they start with Goodreads, because - not everyone might know - Goodreads belongs to Amazon. So, if you befriend reviewers with your author profile, they will most likely not be able to submit a review for your book, especially if it's a good one. Amazon just crosses them off as biased, even if it isn't. So: don't accept friend requests from readers as an author!
Goodreads is nice enough not to inform a person about an ignored friend request.
Rather use an author profile on Facebook to befriend your friends, because Facebook won't give Amazon such information.... yet, UNLESS of course you have connected your Facebook account to Goodreads, that's a different kind of story. If you have, go to your Goodreads account now and make sure that you do NOT instantly transfer accepted friend requests from Facebook to Goodreads.
Also make sure that your reviewers and yourself do not live in the same household. Amazon can track the IDs and simply will believe that you created a second Amazon account. Not using the same shipping address should be a no-brainer.
The only reason to avoid Amazon from banning your friends to review for you is to make sure that there is no digital trace between the two of you. Never use your friends wireless connection for Amazon and Goodreads and vice versa. Don't loan books. Do not send each other presents.
Also: Make sure that your friends review other authors, too! Have them give you a worse rating but a great review. Sometimes a four star review gets accepted, but that depends on the connection you two have.