This issue can be summed up as "What's in it for me?" Is it worth it to print plastic cups? Is the convenience of having something in one day via 3D printing (as opposed to two days from Amazon) worth it? Can it be made cheaper than what is currently available? These questions will need to be answered to establish a lasting market. If there is no price difference and the time to have the part in hand with a 3D printer is almost the same as two-day shipping, what is the differentiating feature?
The main differentiation, other than novelty, will be the fact that items can be customized. I see significant opportunity for vendors to provide customizations, similar to what has been seen with Google's Moto X phone. I believe there is still work to be done in this area. Sadly, most of this will likely be done by marketing groups and will do little to provide actual value to the end user.
This leads to the last challenge: materials. How many of the things you use every day are made only of plastic? As I scan my desk, I can find only a few very simple objects made solely of plastic. Try right now, and see what objects you can find in front of you that are made only of plastic. Would you want to make any of these with a 3D printer?
Plastic makes up a significant portion of many of the devices we have, but they would not be complete without other materials. Even if there were a low-cost 3D printer that could print parts out of metal and plastic in fine detail, it would be able to create only one object sitting on my desk: a twist tie.
Once again, though, I see opportunity. The solution could be an ecosystem where complete kits of components that could not be fabricated via 3D printing (such as electronics, seals, and bearings) could be marketed. The value proposition would have to be customizing the device in some way via the 3D printer. This could establish a new business model for some manufacturers. To do this, though, they will need to find ways to increase volume or profit margins for these kits.
I see a future that could be bright for 3D printers in the home. It seems that there is significant interest in making this work from the standpoint of consumers and manufacturers. I still see hurdles that may yet derail the effort to make 3D printers as popular as 2D printers. I anxiously await the time when I can have a stereolithography-type printer, and perhaps even a selective laser sintering metal 3D printer, all for a few hundred dollars or less. Unfortunately, I do not think that I am a very good representation of the average consumer. My skillset already allows me to fabricate my own designs without 3D printing, and I can fluently navigate more than one MCAD product.
My main fear is that people will become disenchanted when all they can make are toys and novelty items. Hence, I am trying to ask these questions in the hopes that we, as a community, can begin to find answers to these problems and head them off sooner rather than later. I see that the current market is on a fad trajectory. If these questions are not resolved quickly enough, general users could migrate to the next fad. This will mean that the major manufacturers will no longer pursue this market. If this happens, many of us who are anxiously awaiting the day of cheap and high-resolution 3D printers may have to go it alone.
Please share your thoughts. How can 3D printing avoid these pitfalls and progress to the point where 3D printers are as popular as 2D printers?