EA is reporting that members of Iran's military haven't been paid in the last month.
It's surely not the only reason they are becoming disaffected. Other elements that the regime could rely on in 2009 (the working class, the religious) may not be so reliable now should the volcano erupt.
Without those elements the regime lacks any equivalent to the limited if reliable base that has kept Assad afloat so far (Alawites, Christian, Druze). Where is Iran's equivalent?
Finally, a failed economy remains a political problem not only because of its present harsh consequences but because of a now widely shared perception that the problem is incurable so long as the IRI exists and regardless of whether sanctions are lifted.
In a subpost at Enduring America, I analyze why the regime's base has shrunk so badly since 2009 and why the economy can never really recover under mullah rule regardless of whether sanctions are lifted. A recent article on Tehran Bureau showed why the latter may be very hard to do--even if the IRI met every demand on nukes--for another reason.
You'll find that subpost/analysis in Iran live coverage report at enduringamerica.com for Friday, December 28. The new format makes it impossible to post the whole article or even a link to it here.
I also recommend you look up an Arab News article entitled "Blogger's Death sparks national outrage in Iran." It includes interesting details of the torture Sattar Behesti endured (like so many other political prisoners. Again, I'd have posted a link if it were possible but this is the best I can do.