Tough turning back...
Just as guys are trying to plant more non-GMO seed due to resistance, cost, or whatever, producing seed pure enough for non-GMO standards is getting nearly impossible. I've talked about the problem of growing non-GMO specialty corn.
I think the standard for seed is 0.1%; my standard for non-GMO is 1% and it can be really problematic, even with big (200+ A) fields.
This is pure hearsay - and I can't even remember who said it, but the rumor is is takes huge fields of beans to bury non-GMO seed corn production in to meet the purity test.
If you have any better info please comment or give me a tweet. [@jwphipps]