In order to support the constructive processing of submissions:
1.) Review the answers that have already been submitted. If someone else has already submitted the answer that you have in mind, please up-vote theirs and refrain from re-submitting. 2.) Don't be afraid to down-vote submissions that you don't agree with. 3.) Please limit each submission to one major point. If you have two ideas, split them into two submissions. If you have three independent ideas, submit three times.
The products that it will be possible to duplicate may be only those for which blueprints are readily available, so it will be interesting if the eventual popularity of 3D printing compels patent-holders to give people access that they wouldn't otherwise be allowed.