I rather think this subject could continue for quite some time.
There are those that teach that Reiki is a very specific method of hand positions and symbols used by those that have been attuned by a Reiki Master.
All the forms of Reiki I know of require attunement. Otherwise, as Crystal Dragon said, it is not Reiki. However, there are those that believe that attunement can and does come from the Divine and is available for the asking. After all... is not Reiki said to have come to earth from the Divine to Dr. Mikao Usui?
My first attunment was from a Reiki master. My second attunement was received directly from the Divine through a book by Reiki Master Brett Bevell. My second attunement was very powerful and rocked my world. Bevell teaches a more spiritual side of Reiki that resonates well with me. I do, however, continue to read and explore the use of Reiki symbols and hand positions and other ways to utilize Reiki.
Just a note... I was under going a Reiki treatment before I was attuned, and my back all of a sudden burst with intense (but not uncomfortable) heat. When I commented on it, the Reiki practitioner said she was trying out a new method of sending Reiki with her eyes.
It is my opinion that Reiki is not a set of specific rules and regulations, but rather a method or healing to be explored. Call it what you will... the Divine will lead.