Although optimization can cause its own issues, on balance it's how manufacturers can best push the envelope of functionality. A generic bus becomes a lowest common denominator -- even if the first version, like UniPro, is overengineered to allow for future needs. Think of how many modern devices are hampered because they still have USB 2.0 ports or 802.11b Wi-Fi. It takes years for that stuff to go away.
Ironically, while Project Ara would let such components be swapped, its underlying bus would become the new legacy that slows down all other parts. Translation: You'll need a new phone anyhow, so why not choose one optimized from the get-go?
A modular chassis is also a barrier to optimization. The size of modules becomes fixed, limiting flexibility in battery size and shape, for example -- those irreplaceable batteries people love to hate give you more juice because they can take up more room and don't have to fit in a specific shape. A modular chassis also eats up space. It's no accident that Google's Project Ara prototypes are substantially larger and heavier than the typical smartphone -- they need the room and weight for both the endoskeleton and the standard-size modules, which for any particular purpose could easily be oversized.
Modularity is wasteful about the very things people really want optimized a mobile device: size and weight.
It's great that the U.S. military and Google are exploring modular technologies and notions like a multipurpose bus and an electromagnetically "glued" assembly. I have no doubt that some of this technology will show up in all sorts of devices -- and they could be used to improve the manufacturing process of the optimized, highy integrated smartphones we prefer today.
But I don't believe that outside a few geeky neighborhoods that we'll see Project Ara smartphones in public use. The rest of the world will buy powerful devices that they can use, not configure.
This article, "Google's DIY Project Ara won't fly in the real world," was originally published at InfoWorld.com. Read more of Galen Gruman's Mobile Edge blog and follow the latest developments in mobile technology at InfoWorld.com. Follow Galen's mobile musings on Twitter at MobileGalen. For the latest business technology news, follow InfoWorld.com on Twitter.