This is cheating, and it's objectively wrong, and in the long run it only reinforces this behavior, and they might start cheating in real life too. And cheating is a very serious issue, it ruins families, which in turn tremendously screws peoples lives, including and especially children's. Just think twice before suggesting such services to your friends - do you want to be complicit in it all or not? I think a good friend would never do such a thing.