Prediction: Iran will be in a civil war at least as intense as the Palestinian and Iraqi civil wars by the end of this year.
Physical Evidence: A significant car bombing and the inevitable failure of centralized economies, with all that implies (and that implies a lot).
I freely grant that's not a lot to go on, although it is telling that we've heard about these things. The real reason I make this prediction is cultural: The entire culture has been built on the premise that if you have a grievance, it's acceptable to bomb people. No, it's beyond acceptable.... it's your moral imperative to bomb them.
This trigger-happy attitude was "designed" to be pointed at the West and other external enemies, but "the proper way to resolve conflicts" is not something that can be so carefully "pointed", especially in a tribal society where anybody not in your tribe can become "external" in a single poorly-chosen word or slightly disrespectful act. Once tensions get to the sparking point, Iranian culture will have little or no capability to contain the resulting fire, until it burns itself out.
Live by the sword, die by the sword.
I'm a little more optimistic than Glenn Reynolds that letting Iran fester in its own pus is a deliberate strategy by the Bush Administration; it borders on the inconceivable that nobody is paying any attention to Iran. Based on my incomplete knowledge, and taking into account the political climate in this country, it is the plan I'd favor, perhaps with some small, but carefully chosen covert ops to help things along. Iranian culture is brittle right now, and anybody with eyes in the year 2007 can tell how well centralized-authority economies work.