Stuart, your guess sounds right. If peak oil is a reality and close, then shutting in production makes sense because the overall trend has to be upwards. It's a smart move, for the Iranians at least.

What does that do to total current global supply though and how will such actions impact total global supply, and by extension global price? I'm just guessing but wouldn't that serve to drive prices up further given that supply and demand were barely matched already?

What happens when more oil exporting nations (particularly those with substantial and/or growing domestic consumption) start using this line of reasoning and slow down oil extraction?

That doesn't sound like very good news for oil consumers to me (to put it mildly).

No, slowing production is not good news for importing consumers. And add in a similar issue you hint at: many countries will probably continue to pump, but hold the production for their own domestic use. It's a key question: is oil becoming less fungible?
This is an excellent example of why I've been arguing for a long time that you can't apply the conventional production peak model that works reasonably well for individual fields or countries or regions, to the entire world.  As we approach the global peak the decision makers in governments and oil companies know that we're approaching the peak, so it alters their behavior.

The sum of these effects will be to flatten out the production curve--the peak will be at a slightly lower productino level and arrive a bit later.  (At a macro level it's essentially the same as a worldwide tax on oil that reduces demand pre-peak.)

In fact, I think it's good news for almost everyone, as it increases both price pressure and public awareness of the PO issue earlier (both leading to greater demand response), and it also gives us at least a little more time to respond.

PO will still be nasty, brutish, and long, but I'll gladly take whatever early price signals we can get.