It's a funny thing, criticism. Sometimes it's needed, but most of the time it's just another way to let the author know that their work has fallen short in the eyes of one single person. It's a true shame that so many authors take it so seriously.
Criticism is the reasoned evaluation of a text; it is meant to inform, and to correct, and to show the author where they have succeeded and failed in the context of their work. But I find it so hard to read criticism and take it seriously, wherever it is being applied. My reasoning is thus: how can a person offer an evaluation of something they have never done themselves?
Amazon.com offers the opportunity for people who have read books to review them, and post about what they thought of it, what they liked or disliked. They let people criticise the author's work. Some of it I feel is useful, but again... my one thought is "How can they say this? How are they so sure this thing is good or bad? They have never poured their blood and sweat and soul into a story, never struggled with character and plot and theme."
This is not to say that people cannot have an opinion on books and writing. Far from it, of course - I'd hope that people would be willing to tell me about how they feel when they read something I have written. But to me, the opinion of another author is worth a thousand of those who have never written a word in their life. They know what it is to suffer for the art. I trust that when they point out something is wrong, it is something that I must examine very closely indeed. When an average reader points out something wrong, it may simply be that they have not picked up on what I am trying to say.
The flip side to this is that I value praise from an author above all else. When a published author read something I had written and declared that it was good and worthwhile, I felt exalted, vindicated, ecstatic. When a reader told me that what I had written was good, I only felt pleased.
Criticism isn't going away anytime soon. But I think authors should never take it too seriously, or too flippantly. It's better to accept it for what it is: the opinion of one person who has read your work, and for better or worse, they have told the world.