...there is not a single command in Scripture to plant a church or to multiply small groups. There is a lot of church planting and multiplying of groups going on in the New Testament, but not because the church was instructed to do so. The reason that groups and churches multiplied is because the first generation of Christians was obeying Christ's very specific and simple command to make disciples. When Christians are obedient to this single command, it results in the multiplying of groups and churches. To attempt to multiply groups and churches without multiplying disciples is not only disobedient, it is downright impossible.
It's kind of hard to argue with that... yet we still seem to miss the point. Why is discipleship such a hard thing to grasp (or, rather, our need to be concerned about it)?
Of course, I don't mean that we shouldn't plant churches; but we shouldn't put the cart before the horse.