A) A repressive insular regime, ruling
B) a very young population that
C) is increasingly 'wired' to connect them to the outside world, and to each other
Given those criteria, which Middle Eastern countries might be the next 'domino' to fall, if a wave of democratic Islam starts building?
Egypt is a likely suspect. In 2005 21% of their population was under 25 (as compared to Iran's 25%), and the government's suppression of bloggers expressing dissent are well-known.
How about Syria? They were at 23% under 25 in '05, and they too have cracked down on bloggers and social networking sites.
Libya was also at 23% under 25 in '05, and like Iran they have a nominally democratic facade added on to Qadhafi's dictatorship. His efforts to normalize international relations with the West don't seem to have been matched with much of a change to the country's internal policies.
The fact that there are so many countries who could, on a surface examination, be inspired by events in Iran just underscores how important a new revolution could be.