Iran's support for the Shia uprising in Bahrain has backfired. Several prominent Shia political groups in Bahrain have now backed the Sunni monarchy that has long run the tiny kingdom across the Gulf from Iran. While the Shia are a majority in Bahrain, they are also Arabs, and can't help but notice that Iranian Arabs have long been oppressed, and that Iranians tend to have disdain for Arabs. In this case, ethnicity trumps religion.
The Shias certainly appreciated some help from Iran, but they don't have it so bad in Bahrain that simply becoming a subsidiary of Iran seems worthwhile.