However, I am now going to witter at you again, because some of the response in my comments and elsewhere made me think I was unclear. Or possibly, I just wrote A LOT and people began to skim. (This is understandable. I often write excessively long things. My editor weeps with you!)
So, a couple of things I wish to clarify.
1. Many other people write negative reviews, and I think that is a good thing! I cannot, because I feel guilty if I feel I've gone overboard with the mockery (which I always do) and I also feel guilty writing bad reviews considering the fact that I am a total wuss about reviews, and not being able to take my own medicine makes me feel as if I should not be dishing it out.
This is a personal decision and in no way The Only Possible Guide for Doing Things Correctly.
2. When I say I only write positive reviews, I mean I will only write a review if I love/very much like a book. (And sometimes not even then, because I am lazy, and never have enough time.) I do not mean I would ever lie and say a book is fantastic when I think it isn't. I would never do that. Books are much too important to lie about! If I say I like a book, I liked it. (Others may think a book I liked is awful: this happens. Many people think Ulysses by James Joyce is a great book. I disagree! Disagreements happen: this is not news to anyone.)
3. I review books written by my friends, by my critique partners, by friendly acquaintances, by people I don't care for all that much, and by total strangers. If I read a book and I liked it and I have the time and the urge to review it, I do so. I have both had the thought 'Oh, I don't like this person, I don't want to recommend their book' and the thought 'Oh, I do like this person and people know I do, maybe people won't believe I love the book,' and in each case I have recommended the books anyway, and I feel it was the right thing (for me personally) to do.
I am not saying I am magically the only person in the world born without prejudices. I have prejudices: we all do. Anyone can end up prejudiced by a book because they're having a bad day, or by its subject matter, or because of its cover, or for a hundred thousand reasons. But I try to be objective, which is as much as anyone can do.
I get that people are more wary of recommendations of books by friends of the authors, and I get why, which is why my book recommendations tend to have long lists of what I thought was awesome and why I thought so, instead of just being 'It's awesome! Buy it - I COMMAND you!' But I think feeling I can't write reviews of books by people I know is very close to feeling I can't write any reviews at all because I'm a published writer. (Rachel Manija Brown has a post about why she writes negative as well as positive reviews here, and raises other points of complication about being a published writer who writes reviews.)
Like anyone in any field, you tend to get to know others in your field. With writers you don't admittedly have a Communal Writing Office (I kind of wish we did), but you meet them at conventions and appearances and get to know them through their blogs and your blog and email and twitter. So - what if you write a review for an author's book and then you get to know them? Should you take it down? Maybe it's okay and you can leave it up, but you can't review any of their other books now you like them! Wait, that seems harsh... How close are you to them, anyway... Maybe if you avoid them for a couple years. Maybe if you wear a really big hat at the next convention...
That way madness lies. So to an extent you have to go: I trust my own judgement enough when it comes to books to be able to write recommendations regardless of whether the author is My Nemesis or my Great-Aunt Jemima. And the reader either goes, 'I trust SRB's judgement also!' or 'SRB is away with the fairies, I will never read a book she recommends.' Either way. Their personal decision, and my personal decision.
And Now To Segue To Something Slightly Different
So you may have noticed that I have said 'personally' 'for me' 'personal decision' and variants along those lines many many times in this blog post!
Which brings me to another point. When you're writing blog posts about being a writer, the longer you are a writer, the more what you have to tell people about your career is more personal experience than advice.
For example, the vast majority of those who are or want to be published have to write a query letter, so my blog post about writing a query letter contains some advice as well as plenty of personal experience. I definitely suggest there is a wrong way to do it. (My way involved setting fires, so I should know...)
Tobias Buckell has written a most excellent blog post about one's career becoming more and more individual here, so I do not need to repeat his points. Of course, I am in no way mid-career: I am a baby author with one contract, and who knows if I will ever get another! So I'm still very much at the start, but being a little way in does change things enough so that most of my rules are personal rules. They can't be taken, and aren't meant, as advice, because stuff that works for me will not work for everyone! Every writer I know does things slightly differently. (One starts books on chapter two. One makes collages for her books. One responds to criticism really calmly, thoughtfully and well. None of these ways make any sense to me. But they work for them!)
If the personal stuff helps you, I'm really glad! But when I tell you how I do things and why, I do it because I like chattering on the internet and I hope people find it interesting, not because my way is the one true way of righteousness.
So in summary - this blog is about my personal experience, other people's are different, and equally valid! And as an apology for writing two super-long blog posts about online book reviews in two days if you can think of general advice you would like and you think I might possibly be able to assist you with, or personal stuff you might find interesting/helpful, mention it in the comments! And I will do my best.