Yvain: It might be a good idea to start looking for marketable non-apples, but you can't sell generalized non-apples right away. The situation in question is the opposite of what you highlighted: non-apples can act as semantic stopsigns, a Wise and mysterious answer rather than a direction for specific research. Traps of the former domain aren't balanced out by bewilderment of its negation; it might be easier, or it might be much worse.