[MatthewPhillips]

There are more than one layer of closed, and you're right, that layer has always been closed, but from the software side it's a new phenomenon. Pocket PCs and Palms did not share the modern security model. Apple gave us that.

[protomyth]

If the phone OS originated on a PDA, it wasn't locked on the phone version, but for all the other phones, it was a serious PITA to get software out there. Remember BREW and the costs to deploy / get approved (that was the easy one).

Apple didn't give up that. Apple followed the non-PDA path.

[adestefan]

Apple has also repeatedly said that iOS upgrades have been delayed because of carrier review. Same for Google Nexus updates. We all know the disaster that has been 3rd party Android updates because of vendor and carrier review.