Do we need more churches?

I was interested this last week to read of Saddleback and Rick Warren's initiative to plant churches in twelve major cities worldwide including London, it has also provoked an interesting reaction and discussion about the need for such a thing.  Will a new church just weaken existing churches?  Will it be done in consultation?  Is there a need?  Why not just support existing churches?  etc...

We need to recognise a two things about the UK and ask a fundamental question about church planting in the UK; firstly the UK is now a largely unreached people group with the gospel.  Secondly the UK church-going population in general is both ageing and in decline.  And thirdly we need to ask the question do most church plants win new people to Christ or do they simply recycle the flock thus weakening the church?

I think all new church plants would say that the two facts about the UK and the gospel are what drive them to plant, but I wonder if many church plants fail to reach new people and instead recycle the flock, thus weakening existing churches either because people move from one church to the new church because it is young and vibrant, or because it is simply something different, or just that it is a brand of church that better fits their needs (consumerism), or by simply spreading out the pool of Christian students coming to a university city or town more thinly.

Now I want to say right away that some churches need people to leave them, if they are not teaching the gospel, if they are not growing disciples, if they are not encouraging people to serve, and if they are striving to reach out to the lost around about them.  Those are churches I want people to leave, if they cannot reform them and the leadership and membership continue to resist and refuse biblical change!  But what about those people who leave good bible teaching but small churches to go to the new church, thus weakening the gospel work being done at those churches?  Does church planting then help to reach a town or city or undermine the reaching of a town or city?  Is there any point planting a church to reach an area if in doing so we shut another or disable a church which is gospel centred and bible teaching?

I wonder if those who plant ought to have a stringent interview process with any newcomers who are from existing churches?  Why do they want to leave?  Why do they want to join?  Are those gospel motives or merely consumerism?  Ought we to seek to meet with existing churches and their leaderships to discuss this and how we can minimise the impact on existing churches?

I know that people will instantly say that you can't force someone to go to one church and not another, and I'd agree but we can not make it easy for people to church hop, we can make people stop and think.  After all no-one church plants because they want to recycle the flock, or because they want to damage existing gospel centred churches.