As the quality of counterfeits improves, I wonder: would you care if your opponent openly used counterfeits? Is the most important part of your enjoyment of M:tG that you and your opponent actually bought or chanced upon the real cards, or is your enjoyment primarily about the gameplay and deck building? If the latter, I wouldn't care where and how my opponents got their cards, as long as they looked good enough and weren't distractingly badly printed.

I understand WoTC going after counterfeits, because it's their business. But players? Who cares how much money your opponent actually spent, as long as you're both enjoying the game? This is WoTC's problem, but it shouldn't be the players'.