You're likely to meet the authors you review, whether it be through email, online forums, or a writer's conference. If I get a book published, I will belong to the ranks of CBA novelists whose books I praise or bash. If I hate a book and my review reflects it - what if that's the author who could have recommended me to her agent? Or what if an editor who also hates the book reads my review - will he remember my name for the future?
As a longtime reviewer myself—CDs, movies, books—I understand her pain. (And am relieved she seems to like my fiction ... so far.)
P.S. -- Despite the sing-songy title of this blog entry, it is technically not a "bad review" but a "negative review." At one of my previous magazines, there was one particular associate publisher for whom I had to constantly explain the difference.