They make no sense, for two reasons:<p>1) hardware engineering: there is no dead space in a phone, every single square inch is used by something. The PCB is as compact as possible. If you design a modular phone (like project Ara), you easily double the space required. Instant losing proposition: less efficient, more bulky.<p>2) market: even if you offered a wonderful selection of decent modules, market reality means that 90% of your customers would use no more than 2 or 3 different configurations, at most. If that's the case, forget about modularity, just build those 3 configs and optimize them to death.
They only make sense to me if all the functionality was based out of a single (or two) type of unit. Camera/Ram/CPU/gps/etc was all just a matter of software. Need more memory? Buy more phone-goo, designate it as RAM, and bam. Basically computronium.<p>So, in conclusion, completely unrealistic in the near term, or our lifetime.
If my smartphone were modular in the same way as a desktop PC, I would worry that minor bumps would cause disconnections or shorts. In theory I'd love to upgrade parts at low cost, e.g. upgrading to an AMOLED screen, but ease of disassembly doesn't seem compatible with the durability/weight/size requirement of a device I carry around all the time.<p>In practice, it's easy to buy a new phone every 1-2 years, and give the old one to a relative.
Big Flop. Modular smartphones provide iterative benefit not revolutionary. Until you have revolutionary breakthrough in product (more software than hardware since hardware is easy to be cloned), these will remain as toys.
Ultimately depends on marketing, consumer reception, how well developed the product is and how overall user experience is. I think that's really what would either make or break it.
Dead end. I suspect a widely varied yet cross-compatible & long lived set of modules & interfaces would leave us with a gigantic / expensive / ugly device.