I concur with LambdaFF. I dispise cloud based services. I too think that perhaps its because I am old school. I hope 3D printing doesn't go entirely in the cloud.

As for going mainstream. The simple reason is that it is still too expensive, 3D printers are not exactly cost/time efficient. If I need a replacement part, I go to the store. I'm not going to print it out for 14 hours. Once 3D printing can hit a point where we can purchase SLA printers for under $400, and print at speeds that are quite a bit faster, that's when I expect it to go mainstream. Not a moment sooner though.