When Ekklesia pointed out that the Church of England appears to be involved in the dodgy market dealing it rhetorically condemns, the main point of our argument was that the churches have a golden opportunity to invest in something much more exciting.
Unsurprisingly, many picked up on the 'negative' angle: "church accused", "hypocrisy", etc. But though the tendency of Christians to preach virtue to others while not examining their own behaviour too carefully remains a problem in this and other areas, the real issue is that the "global economy of the churches" (worth billions overall) could and should start to act very differently - putting into practice the Gospel values of sharing, equality and primary concern for the poorest and most vulnerable. We can make those decisions ourselves, or at least many of them. We do not have to wait for permission from "the market". Some will be costly and difficult, of course. Many others will involve backing the whole mass of small-scale alternatives churches and faith groups are already involved in fostering. Oikocredit is a good example. http://www.ekklesia.co.uk/search/node/oikocredit 
The alternative values the church that seeks to be the Body of Christ in the world can and should be enacting, would constitute a powerful contribution to necessary larger arguments about the reform of regulative financial systems, the operation of markets, and so on.
Economics is a profoundly theological issue, because, as Jesus is recorded in the Gospels as having pointed out: "Where your treasure lies, there lies your heart also." Indeed, Rowan Williams was correct yesterday to pinpoint the issue of idolatry  at the heart of the current system: the attribution of ultimate worth and value to things that are purely instrumental and should have no such claim to control our lives. Both the economic and spiritual issues are raised in the detailed paper I produced in 2005, Is God bankrupt?  This was a response to an ecumenical report which tried to get the British and Irish churches to "cosy up to the market" in a way that was just as simplistic as some alleged earlier ecumenical attempts to dismiss markets completely. There's also a summary of issues and initiatives involving church and economy, called An Economy Worth Believing In .
So this is not something we have just this moment decided to stick our noses in, before Paul Vallely and others are tempted to trot out that accusation (as they wrongly did over the reform of faith schools question). Hugs all round, then... and let the debate continue.
(Paul's 1990 book 'Bad Samaritans: First World Ethics and Third World Debt' and his subsequent work, including material for Live 8 and the Africa Commission, is very helpful, by the way.)