Aikido might have a false reputation of being soft and safe. I have practiced in the past Judo and Thai Boxing for many years and never witnessed or heard of a deadly or near dealy incident, untill I started up Aikido. In my understanding, Aikido is the only MA where someone gives himself willingly without resistance for another person to apply very dangerous throwing and arm/wrist locking techniques. During this year, I have witnessed a huge (1.90 meters and 100 Kgs) 2 Dan black belt throw a 7 Kyu (out of 10 kyu at our school) student with a Kokyu Nage and kept holding the arm untill Uke landed very heavily and almost vertically on the top of his head. We all feared for our friend's life, as he was unconscious for a few minutes. He went later to the hospital, had to wear a neck brace for 1 month, and ever since doesn't want to hear anything about Aikido. Of course the second Dan student is still throwing people around almost carelessly (I say almost because he has been reprimanded severely by Sensei, but some people are just mentally sick and cannot stop hurting others).
Anyhow, it would be interesting to know how many of this site's visitors have actually witnessed such accidents in order to establish some kind of pattern of frequency or severity of accidents.