Split Personality. RJ is Patrick Jane himself since no one in the 7 suspects matches RJ’s criteria 100%. 

Brett Stiles, Gale Bertram, Sheriff McAllister, Ray Haffner, Reede Smith – either too old, bald, fat/big, no power/not smart enough like Jane. Robert Kirkland and Brett Partridge – can be any of the two but too obvious and still not convincing. They’re all RJ’s allies for sure. 

If PJ is RJ, it would be great.
-can match RJ’s description
-the smiley face looks like Jane
-RJ likes tea and reading books like Jane
-RJ is smart like Jane (same level)
-it doesn’t show much of PJ past
-PJ can manipulate/control one’s mind
-RJ can read PJ’s mind (because they are one)
-PJ has been in insane asylum
-only PJ can know about his childhood memory
-why all the ally of RJ that was caught always dies or something…
-the only conflict for me was the scene ‘tyger, tyger’ the only ep. RJ appeared (was PJ hallucinating?)
-it didn’t show the killing of PJ’s wife & daughters while he was a guest in a show. (PJ could kill them first) Why PJ would kill his own wife & daughter??? Simply because he’s sick (split personality) and doesn’t know about it. That is why it’s MENTALIST.  

Anyway, Mentalist is so good. We are all watching it from Philippines, Sweden, Cyprus and Japan. We can’t wait to see more. 

Red John, please reveal yourself. You are the talk of the town!

I think RJ is Patrick Jane. Because after his Family get murdered by 'someone' , he needs aim in life to live. May be he is not doing knowingly but whatever it is he is RJ. And he is just using style of 'someone' to kill people in the name of RJ

I think Patrick is Red John.  Maybe he had a nervous breakdown and killed his family. Maybe those days he was broke. He was in a mental hospital. And began see things. Maybe he is schizophrene. It could be. We can only guess.

Please note, that I don't think it's Jane, and posting it on Jane's theory on purpose, to prove all of you wrong.

Reasons why Jane isn't Red John:

I will start with easy ones that prove almost nothing

1) He shook Red Johns hand. Since he can't shake his own hand - it's not him. Anyone would respond -   Jane might have a split personality, and RJ made Lorelei tell Jane that it's someone he shook hands with to throw him off the trail, or start another sick game of hide and seek. Possible... Unlikely but possible.

2) Kirkland steals Jane's notes. He might be Red John, might be one of his pawns or a secret investigator. If we assume he is either Red John or his pawn (Because the last one is very unlikely) then comes up the question, if Red John is Jane, why would he need his notes? Doesn't he posses all the memories Jane has?
In case you tell that he doesn't share Jane's memories, you will then cancel out your hardest evidence - The fact that Red John allegedly read Jane's memories to kill his happiest one.

3) We know that what drove Jane into the Red John investigation are the death of his mother and daughter. To assume he is Red John is to assume his other personality killed his family to start the chase. You may say that it's exactly what happened, but as far as we know, Jane was mentally stable before the murder.

4) (Connected to 3) Jane's family was killed while he was doing his act of TV. To assume Jane is Red John is to assume he hired someone to kill his family, or he was at two places at once.

5) And the hardest evidence to prove Jane's innocence: His happy memory (Aylin - not sure how it's spelled) was murdered overnight, or afternoon the previous day (Inferred from when the maid found her) Since we are shown footage of Jane sleeping in the office during all previous day and through all the night, he could not have possibly killed her.

So here you go - 5 reasons why Jane isn't Red John.
Note, I didn't name all the reasons. Follow the same logic, and you will find more proof.

I do believe that Patrick Jane is in fact Red John and believe I have some fresh insight in this case. As we all know, Patrick is very well-read person. He knows the entire play Hamlet (S04E20), and Jane very cleverly misquoted Macbeth and Philo fell guiltily into his trap by correcting him that it was “Neptune’s oceans” not “Neptune’s waters” (S04E17). Now, we all heard (S02 final) Red John tell Jane a poem by William Blake: The Tyger. Obviously this was not really Red John saying this, but another accomplice of him. However, we do know that both RJ and PJ like poetry,

I know it's far from airtight, but add everything up (everything being things that were previously said such as both of them being master manipulators, Red John knowing a memory from Patrick's youth, Patrick's frequent daytime napping, Red john knowing the 7 names and Red John always being a step ahead of PJ) and I believe it is safe to assume Patrick Jane as Red John. I do not believe PJ is aware of his alter ego, but I do believe RJ is aware of his alter ego.

As with many wih Schizophrenia, one personality may know of the others existence but the other has no clue. Red John knows he's Patrick, but Patrick doesn't know he's Red John. He's charming enough and clever enough to get people to do his bidding. The childhood memory that only he knew about the girl murdered last episode sealed it for me.

I honestly dont think the writers could justify making red john anyone other than Patrick. He obviously has an incredible mind capable of handling multiple personalities. Im not sure if he developed the red john personality before or after his family was killed. However i think that patrick developed himself into red john to torture himself because he blames himself for his family's death.