I think red john could be one of four persons - Bob Kirkland, Brett Styles, Kristina Frye and Walter Masburn. Brett, Kristina and Walter are charasmatic persons who Patrick Jane likes (I refer to the comment Lorelei made about RJ and PJ being similar and she cant understand why they are not friends).

Although I don't find Bob Kirkland likeable, has anyone noticed that when he shook hands the first time with PJ he placed his hand on PJ in a similar manner to what PJ does when he hypnotises people?. He also did that when they met at the hospital after he killed Lennon. I think this is significant.

I think that initially RJ hypnotised PJ when he was institutionalised after his wife and daughter's murder (we do not know who visited PJ then) and I think that Bob Kirkland laying his hand on PJ is reactivating the hypnosis - maybe PJ's happy memory was planted RJ in the first place?