I don't like the power struggle that gets set up with 'no' which is why I turn it into a game. I don't want to fight them and so I find it breaks the ice a bit if I don't rise to the challenge. I also think it doesn't leave them with the idea that something isn't going to happen because they said no. It plants the idea that it is happening just not in a way that is forceful. There are times that I don't have a choice whether they yell no or not - like when it is time to go home from somewhere and they say no. I give them more time if I can, but sometimes we have to go so I do the whole 'ye-eah' thing and then explain to them why we need to leave - 'The shops are closing and it's time to go' or 'DD2 needs to sleep and we need to get home'. It usually works pretty well but it isn't foolproof (nothing in parenting ever is) but it is a good tool for the kit