Good news for users means trouble for developers.

As Apple has demonstrated, one of the dangers of innovating in the smartphone app market is there are no guarantees Apple won’t borrow your innovations and bake them into future iOS versions. (To state the obvious, there’s nothing stopping Google either.)

We exchanged a few sideways glances here as we watched Apple show off the “read later” feature in iOS 5. It was obviously a direct answer to the Instapaper service. Then there was the camera feature that uses the volume keys as a shutter button, a duplicate of the third-party app Camera+ that Apple blocked from the App Store in 2010. The New York Times has gone deeper, providing a round-up of coming iOS features that borrow features from popular iPhone apps like Camera+, Zinio, and others.

Then where is the opportunity? Doing what Apple can’t.

In a thoughtful response, Instapaper founder Marco Arment describes how Apple’s move makes an obscure feature more mainstream, and may actually create demand for a cross-device “save for later” feature. While Apple can provide the feature across iOS and Mac OS devices, Instapaper is poised to do what Apple can’t – bring it to a much broader landscape of handsets, tablets, and the web.

In 2007 the iPhone toppled the carrier controlled walled-garden. Now iCloud and other iOS features add more bricks to Apple’s own walled garden.

Zoom back out to the macro view for a moment and you can see some irony. Apple is credited for breaking down the carrier controlled walled garden, introducing mobile consumers to mostly democratized App Store™. Apple has their own walled garden – a tidy, controlled ecosystem of devices, media and apps. Irony aside, nobody can blame them – it’s not just smart, it’s working, and users have a much better smartphone and computing experience than they did in 2007.

So where is the opportunity? Well, Marco is right. Apple will continue to build it’s self-made ecosystem – powered by the formidable iCloud and iTunes duo – and perfect for people who buy wholesale into Apple’s ecosystem. But lying beyond Apple’s controlled area of the market is plenty of unfettered opportunity for others – manufacturers, software developers, media and publishing brands – to enable interplay, collaboration and connection within the entire expanding consumer electronics ecosystem.