This was originally going to be a generally phrased question about gaff cards, but as I started typing I realized that the real problem I had was not the use of gaff cards specifically, but the ability to perform tricks while spectators who have seen you perform before are present.
Gaff cards cut down on your ability to repeat a trick in front of an audience. Take for example the 'inked' card out of UltraGaff, or the inflated Ace of Hearts out of Arcane gaff, because the cards are so amazing the effects they produce leave such an astounding impression on your spectators. This means they will remember that trick forever, which means you aren't allowed to ever do that trick again if that person is nearby. They'll remember it for sure, and remember that the card that this new person "freely chose" was the exact same card that they supposedly freely chose when you did the trick for them a month ago.
While I do often do tricks for strangers who I never see again, magic has also made me a lot of new friends. Stigmata is probably the hardest hitting effect I do. Which means I cannot tell you how many times I've been doing card tricks and had a friend come up and say something like "OMG DO THE ONE WHERE THEY GRAB YOUR WRIST". For anyone that performs stigmata, you know that them saying this just made that trick 100 times harder to pull off. I have to say though, I don't give in to the pressure. When that happens I usually shrug it off, say something about not having enough pixie dust on me for that one tonight or something and move on. It really builds suspense for if I want to do it later, after the audience has dismissed it, or if I ever see this person again.
So, to all the magicians out there, what do you guys say? Is there a cure-all for this bug? Some tips, aside from "Learn more tricks, only perform some." Haha.