Ok, I'll bite. I've watched this film many, many times. I would have to say that Neil is ultimately responsible for the choices he made. Keating did encourage the boys to follow their dreams (much to the chagrin of their parents, who put them in the expensive and exclusive school for boys in order to help them get into the best colleges and beyond to be doctors, lawyers, etc.)

However, in this life we are all responsible ultimately for our choices. In situations like this one where it is a youth and has a tragic end, the parents especially are looking to blame someone else for their failings. They destroyed Neil's will by taking away the one thing he loved to do more than anything. He didn't feel he had any other choice but to take his own life because his life wasn't his anyway. Mr. Keating and acting made Neil realize that possibly more quickly than he would have otherwise, but Neil had no other choice - either be a slave to his father for another 10 years probably, or choose to take his life - and that's what he chose.

I had a friend who committed suicide in HS and his parents were on a rampage trying to find someone to blame or lash out on. It didn't take long for me to figure out how circumstances he was in would lead him to it.

In the end Mr. Keating may have encouraged Neil to explore his romantic/poetic/creative side, but he didn't type a fake letter for him, or lie about quitting, etc... Neil made that bed. Keating was just a scapegoat in the end. He tried to tell Neil to talk to his father, not lie to him. He encouraged Neil to do the right thing at the time. I don't think Keating was a good fit for the school, actually - the only reason he came back there was for sentimental reasons, I suppose. And, Keating would have been better off as a Drama/English teacher where he could expose the kids to that kind of creative thought and expression. His biggest mistake was thinking he could teach those concepts at Helton with impunity.