I imagine this would instantly defuse patent trolling while having no collateral damage to businesseses that actually use their patents to defend investments (which is supposed to be the whole point).
Is the only reason we're not seeing such a law because trolling has a powerful lobby, or am I grossly oversimplifying?
That's how patent law worked until the 1940s. It was called the "paper patent doctrine." i.e., if you're patent was just on paper, and not used in industry, then the patent was dead.
Prof. John Duffy wrote a great paper about it last year - http://cornelllawreview.org/files/2013/10/98CLR1359.pdf
Either a) Using the patent to to produce and sell the invention, in which case it's not a paper patent.
Or b) Using the patent purely to sue other people (which is what most of the big name patent trolls do) and therefore must be stopped.
If they're successful, patent trolls end up with licensees too.
If you're not allowed to sue anyone until you already have licensees, then if you invent and patent something and pitch it to a company, you can't sue them if they rip off the idea.
Most of the patents I have been noticing waved around are "Do something we did 50 years ago... but on a computer". Is the "on a computer" really a definitive mark.
On the idea of 'paper patents', what is to stop someone from registering something barely plausible today that may occur in the near future? Say, something like "3d printed food" where a file that contains the information on the material is structurally printed and heated/cooled. It isn't possible with our current tech, but when someone figures it out 5-10 years from now, you could spring that Jack out of the box and rake in cash.
But the strategy you suggest is sort of used. The patent attorney will keep open an application for years using procedural tactics, and then try to get claims focused on modern products into the patent.
I confronted a rather weaselly dude attempting to patent troll tabletop roleplaying games by filing for a claim on character conversions, with an exceedingly vague 'with a computer' veneer over it. Fortunately the guy had his application rejected twice, and looked due to have it rejected again (as well as having attracted attention from much bigger fish) before he closed ranks and disappeared.
For example - let's say I come up with a much better way to make steel for cars. I patent it right away. Since I don't own a carmaker, it will take a while for me to sell or license it, and perhaps 4 or 5 years for an auto maker to actually use it.
Again, just being the Devil's Advocate.
One can easily see that the idea that patents encourage inventions is just plain wrong - just imagine what would happen if patents were abolished - would inventions stop happening?