Dr. Timothy Keller wrote a very helpful article about church planting and how it is beneficial to local churches and to the Kingdom.
The vigorous, continual planting of new congregations is the single most crucial strategy for 1) the numerical growth of the Body of Christ in any city, and 2) the continual corporate renewal and revival of the existing churches in a city. Nothing else–not crusades, outreach programs, para-church ministries, growing mega-churches, congregational consulting, nor church renewal processes–will have the consistent impact of dynamic, extensive church planting. This is an eyebrow raising statement. But to those who have done any study at all, it is not even controversial. ~ KELLER