3D Printers won't be news for most - these devices, traditionally used to produce physical prototypes from digital models, have over the last few years become more powerful and affordable. They started trickling from industrial design labs into the mainstream (companies such as MakerBot Industries are selling desktop 3D Printers for home users, while its vibrant community of 'makers' shares designs in Thingiverse) from toys to spare parts, even build your own robot models.
The situation resembles the early days of the personal computer revolution, when dedicated hobbyists ordered computer kits such as the Altair 8800 and the first Apple, to put them together in their garages. There are many similarities between the current generation of desktop 3D printers and those primitive personal computers - they are still pricey (Makerbot's Thing-o-Maticsells for around $1,000), have to be assembled by the user and have limited capabilities (not least in terms of the size of the objects that can be printed with them). An open source ethos prevails, like it did at the beginning of home computing. For instance, the RepRap project is developing a self-replicating (i.e. it can print its own parts) 3D printer with a Free Software license, so that users can improve on its design and share it freely.
Perhaps the 3D printing movement is waiting for its Macintosh moment, when mainstream users will become desktop manufacturers in the same way in which, almost three decades ago, they turned into desktop publishers.
It won't happen in 2012 - there were 8 years between the first Apple and the Macintosh after all, and even then Macintosh was a niche offering. 2020 maybe? We'll see. Some may doubt whether this will be a mass market. At the same time, the popularity of online user generated content suggests that when people are given creative tools, they use them, so we shouldn't discount the potential scale of demand. LOLCat statues anyone?
Focusing on the shorter term, I foresee that next year will start feeling like the end of the beginning for 3D printing, with more venture capital investment going into up-and-coming companies (MakerBot Industries already received $10 million this year), cheaper and improved 3D printers, innovative user interfaces for model manipulation (a Kinect plug-in maybe?) and more schools and universities buying 3D printers for their classrooms and labs, thus preparing the next generation of 3D savvy tinkers and makers. We will start to see the frictions too. For instance, DMCA takedown notices from high profile creators of proprietary designs freely shared by users (it's already happening).
And last but not least, by this time next year, I foresee a very substantial probability that you will receive a 3D printed gift for Christmas.