Every morning I receive at least ten pitches from PR agents promising that a company offers something that is new, unique, revolutionary, or better than some other service that I have reviewed. 90% of these emails don't get more than twenty seconds of my attention. Of the ten percent that I do consider, perhaps half lead to me writing a blog post. This is why you don't see me writing negative reviews of a service or product.
Writing a negative review of a service or product isn't a great use of my time or your time. I focus my effort on bringing you the services and products that can help you and your students. So if I don't write about something, I probably didn't like. The exception to that being that there are some products I really like and actually pay for, but don't fit the editorial guidelines of Free Technology for Teachers.