I'm afraid I think it might have. From what I've seen, many users (including me) seem to prefer to stick to their own game and don't usually take part in these challenges, which is a shame, as it means your challenges don't get the attention they deserve. I think people prefer just choosing their own teams and playing with them for however long they want, rather than following a challenge. Maybe for FM11 it might be worth creating a thread with a few 'challenge saves' posted up, and allow users to download whichever save they want to play.