I'm nervous about leaving reviews on books by unknown (to me) authors, because I've seen the kind of drama that some indie authors get into over them.
There's also problems with "
review farms"--I've no idea how this gets arranged, but 43 5-star reviews with no more than 26 words each, none of which mentions a single detail about the plot or story itself, are not useful to me as a reader. (Too long? Look at
Meg Sharp's reviews--scroll down.) And knowing that those exist, makes me uncomfortable saying things like "I enjoyed this; the dialogue was particularly good and the action scenes were hilarious." And I'm not always up for leaving a longer review.