This report is dated, but it is very enlightening when looking at the domestic pressures that have sustained the Bahraini uprising thus far.
As has been stated in the past, the Bahraini people are about 70% Shia with a Sunni ruling regime. However, I did not realize that the Bahraini regime has been allowing foreigners to naturalize within the country for quite some time. These foreign workers have been primarily Sunni and thus the Shia majority feels as if the regime is allowing naturalization to tip the balance of power. There are no official, accurate census numbers from within the country, but this is a significant point of contention for the protestors.
Here is a link to the report. It sheds some interesting light on the protests that continue today in Bahrain.