[CamperBob2]

1. I think the obviousness of an idea might change throughout time.

Sounds like an excellent reason not to allow someone to own the idea for 20 years.

[darkarmani]

Yes, or changing it from a binary system to a continuum that maxes out at 20 years. Software patent? 5 years. New drug - 20 years. New algorithm (can't patent math of course) 10 years.