Although I love Apple's design aesthetic and ability to consistently churn out amazing hardware, I'm never quite comfortable fully embracing it. The reasons have to do with platform fertility, or how well suited a platform is to incremental platform innovations and new platform creation. Onward!

Personal computing

The evolution of personal computing is generally accepted to look something like the following:

Mainframe -> Minicomputer -> Personal computer

The above relationship can be interpreted in at least two ways:

1. The former was disrupted by the latter.
2. The former was used to design the latter.

Taking the first interpretation, we are in the middle (closer to the end, I reckon) of another disruptive innovation:

Personal computer -> Tablet

Indeed, compared to laptops, tablets seem to be a better way for the general public to use computers. The touch interface is more intuitive, and the physical form factor is better suited to casual use. For the purposes of this post, let's assume for argument's sake that tablets overtake personal computing in the future. The interesting thing is what happens next:

Tablet -> (next disruptive innovation)

Let's go back to the second interpretation: b was designed using a (or, in some biblical sense, b begat a). In other words, designers and engineers used a mainframe to invent minicomputers, a minicomputer to invent PCs, and a PC to build tablets. We can call this "platform fertility" just for fun. Up to now, said professionals could use the latest general purpose computers to do their job, but this may be changing.

The tablet disruption was enabled by its predecessor, the PC, being flexible and extensible enough, and thus well suited as a prototyping platform. Linux, OS X and even Windows are all very flexible platforms, intended to work with a variety of software toolkits and external devices. These desktop platforms never imposed restrictions like software signing, and even if they did, you the power user could always override.

Peril of a closed platform

I don't want to argue about the semantics of the word "open", but regardless of your religious dispositions, we can all agree that Apple is not, nor has any pretenses to be associated with, that word. I'm not making judgements here, it's just how they roll. The API surface is carefully designed to give developers the right amount of flexibility, but not more. AppStore is explicitly a sandbox, and if you don't play by the rules, you lose your playground privileges.

So imagine for a minute that iPad swept the tablet market (shouldn't be hard given the current market distribution). From a pragmatic user's perspective, this is fine, even good! iOS is a very well-integrated platform, working across all shiny Apple products, and users are generally pretty happy with the interface and overall experience. From a curious developer's perspective, however, things are a bit different.

As an iOS developer that wants to improve the platform experience, however, you are pretty much stuck with how things are. You can't replace the lock screen, can't write long-running applications that read in accelerometer data in the background, can't customize your home screen launcher, etc.

The problem is exacerbated when you set out to try to invent the next thing. How do you interface with your new stereo camera rig? How many hurdles do you have to overcome to make it possible to interface with your new smart watch? How about a pair of smart contact lenses? How do you get raw USB access? Bluetooth? Ad-hoc wireless? Granted, the further you venture away from the platform core, the less help you would expect from it. This is generally where you climb down a layer of abstraction - for example, to NDK in Android. Without such an option, you're left dead in the water.

A Litmus test

Unless iPads become more hackable or other, more developer-friendly tablets emerge as serious competitors, laptop computers will become specialized tools for software professionals while tablets supplant laptops for the rest of the public.

Platforms inherently restrict the developer in some sense, placing them in a box delineated by the APIs that the platform provides. An interesting way to examine this box is with this notion of "platform fertility", centering around the question:

Can this platform beget future platforms?

Whether your idea of the next platform is incremental (for example, a better lock screen) or a fundamental disruptive innovation (for example, smart glasses), the answer to the above question for the current state of iOS is a resounding no. Sorry bro!