I considered having the "write something in order to participate in future rounds" rule for Talk Bingo for this reason only: there is a lot of work put into making those bingo cards. And for KB, there are many many more cards being made and so for the investment in time, getting something back is appreciated. I decided against it, but since I'm doing Talk Bingo twice a year I may go with "one fic during posting or amnesty or you have to take the next round off."