Hi Michael,
Ultimately the system is voluntary - Designs are data, and data is functionally free to transmit, so there's a limit to what you can do about that.
I think that's why it's so important to keep prices low, and to have other parts of the service which add value (for example giving you a .gcode version specifically tailored for your printer).
To further dis-incentivize piracy I'd like to see advertisement supported downloads, with a small 1x1 brand printing in a user customizable area of the item (parameters set by the advertiser) - Then there is no cost to the end user, and the advertiser gets branding on something permanent instead of the usual disposables.
I will respond in more length later, about to record the first episode of The Daily Bitcoin podcast.
Also, you might be interested in my latest article releasing later today entitled "The New Renaissance: How #Bitcoin Millionaires will change the world"
An audio reading by the author (me) is available under an open source license here
https://soundcloud.com/mindtomatter/the-new-renaissance-how
Thanks,