I don't WANT Smith to be Red John. But I think that's exactly what Bruno Heller may have done.
I'd much rather have Bertram as John. Stiles, even. Or Ron. Or even McAllister. Resurrect the original Season 1 Red John, Brett Partridge. Hell, go with the silly Kirkland twin idea - ANYONE but Smith.
Still, Smith may turn out to be the one.
A few months ago Bruno Heller said that viewers would be disappointed to learn Red John's identity. Well, can you pick ANY random character from the entire series that would be more disappointing than Smith, the stupid, obnoxious, foul-mouthed troll introduced in this season, or maybe the last one? (No, I don't care if it turns out that "he was only pretending" and "was actually completely different". The persona we got for a number of episodes now is that of an idiot troll who curses. If he's revealed as Red John, then we're forever thinking of Red John as an obese goblin we're used to. That's it).

Additionally, FBI plays a huge role in the "Red John" episode. Well, who happens to be with the FBI?
Smith's character is already listed in the episode, too; it's been prematurely revealed.
Finally, and I think THIS is the biggest reason, he's the least popular choice among the viewer. Thus, he is the least expected one - and that, I believe, would be why Bruno Heller may want to have Red Smith. However, if THAT is his line of thinking, then he's making a disappointing mistake... Smith is NOT rarely named in the "Who's Red John" polls by people as Red John because he is so improbable. No he's rarely named *BECAUSE NOBODY WANTS HIM AS RED JOHN*. Amen.