Recent reports claim that Iraqi Shi'a militant leader Muqtada al-Sadr will be taking up residence in the Iranian religious center of Qom for the next four to five years - he's already spent most of the last year in Iran. While on the surface this appears to be good news for Iraq and its American allies, this may portend real problems down the road.
Al-Sadr is not merely hiding in Iran, he is pursuing his religious studies - he hopes to eventually rise to the status of a marja' al-taqlid (literally, "source of emulation"), and a grand ayatollah. These leaders are the highest authorities in Twelver Shi'a Islam. For al-Sadr to achieve his goal of being the most important man in Iraq, he needs these religious credentials to become the leader of the largest segment of the Iraqi population.
Currently, the mantle of Shi'a religious leadership in Iraq falls on Grand Ayatollah 'Ali al-Sistani and Sayid 'Abd al-'Aziz al-Hakim, both rivals of al-Sadr. Ayatollah al-Sistani is by far the most respected Shi'a cleric in Iraq, but is 78 years old and in poor health. Al-Hakim would make a logical and widely accepted successor to al-Sistani, but the 58 year old leader of the Supreme Islamic Iraqi Council (formerly the Supreme Council for the Islamic Revolution in Iraq) lacks the religious credentials to assume the role. Al=Hakim is in the same situation as Muqtada al-Sadr - both come from distinguished Shi'a religious families, both have lost numerous family members to Saddam Husayn and setarian violence, but neither have the titles to move up in the heirarchy.
The difference between the two is that Muqtada al-Sadr is willing to spend the requisite time pursuing his religious studies in Iran. Al-Sadr currently holds the title of hawjat al-islam (literally, "proof of God"), a rank below ayatollah. Four or five years of study in Qom will almost certainly see him elevated to the rank of ayatollah, possibly even grand ayatollah. The title/rank of ayatollah is conferred through peer recognition of religious scholarship - being from a presigious Shi'a family does not hurt either. The first step in his plan to be the most influential figure in Iraq was the alleged transformation of the jaysh al-mahdi (Al-Mahdi Army) from a militia to a social welfare service. Of course, that epiphany came after his militia sustained devastating losses in battles with American and Iraqi troops.
Encouraging the religious establishment in Qom to desginate Muqtada al-Sadr as a marja'/grand ayatollah will be a smart move for the Iranian leadership. Since he is from a famous and respected Iraqi family and he has a large following in the country, he may emerge as arguably the most important man in Iraq. Not a bad person to have in your pocket.