Posts pop up all over the place asking authors to support other authors. Authors beg for reviews and for people to purchase their books. Pages on Facebook and different Yahoo! groups lists are clogged with authors promoting themselves, and occasionally others, to the point that important posts are lost in the babble.
I believe in supporting other authors. In fact I'll review and purchase and promote other authors' book before I will my own. However, I am tired of asking for reviews for my book or books and being told by other authors (including one whom I've supported over the years), "Oh, I don't review other people's books." Yet, those same people expects us, including me, to review their books.
I have supported other authors by buying their books, until I discovered that even those I thought were friends never bought even one of my books. Now, I'm much more stingy with my limited income when I choose books to buy.
Have you noticed among all the self-promotions on social media that some people promote others, while others promote only themselves? Yes, it becomes quite noticeable after a time. I will share and retweet and give notice for other authors if they in turn do the same for other authors and, possibly, for me.
I love reading, but now I read books I want to read or ones sent me to review. However, I have stopped reading some authors whose work I enjoyed in the past (and whom I know personally) because of their "buy my books but don't expect me to buy yours" behavior.
Supporting other authors, or illustrators, is good, but that support should never be a one-way street.