Please don't let the abysmal manners of one awful person dent your kindness and generosity. But put out signage that says "Limit 1 per variety and 2 total" which then gives you the opportunity to say, to NICE people, "You seem like a great gardener; why don't you take two or three more?" That person feels as though they got a freebie based on the quality of their person and will replay that nice little moment for the rest of their day. Plus you have ammunition for the hideous people. "SORRY, it's LIMIT TWO TOTAL [you absolute pig!]"