One of the foreseeable problems was pointed out by, amongst other people, Cory Doctorow at CCC Congress in 2012 [https://www.youtube.com/watch?v=yYqkU1y0AYc]. Basically, these devices are comparable to MP3 ripping software, but for things.
According to Doctorow a new copyright war could be upon us, and this time we're pissing of more powerful lobbying interests.
A lot is possible, but in my experience it's often just too costly to be worth it. The medialab I work for explored this issue last year: we copied a euro-coin with a metal 3D printer. It worked great, except that it cost 30 euros to do.. [http://kunstroof.setup.nl/ (Dutch)]
