John von Heyking is concerned about Iran, and not only because of their nuclear ambitions. He thinks that President Mahmoud Ahmadinejad’s words and actions are very much worth watching, especially regarding the return of the Twelfth Imam, which is very important to Shi’ites.
While the issue is complicated, von Heyking’s piece is very clear (also good links). His last paragraph:

"Western observers need to be able to understand the ideological and religious overtones of the current situation in Iran. Ahmadinejad’s peculiar references to the Twelfth Imam are no mere eccentricity to be taken lightly. Nor do they seem to be the rhetorical ploy of a politician manipulating the excitable masses (as some have interpreted Saddam Hussein’s embrace of Islamism in the later part of his rule). Minimally, Ahmadinejad’s speeches and actions portend a constitutional crisis for the Iranian regime. Maximally, there are times when one should take bombastic statements not as double-talk, but for what they are."