They would probably argue that confidence ranges for the permanence of geological storage are quite high (especially compared to other uncertainties in climate policy e.g.temperature increases over the next decades) – see their report on this issue here:
http://www.cslforum.org/publications/documents/geostoragesafe.pdf . The insurance company Zurich recently launched a carbon sequestration liability insurance product, reflecting what must be a farily high level of confidence in our geological understanding of carbon storage.

The uncertainties around CCS exist in the context of some fairly uncomfortable certainties, including the fact that coal remains an abundant and inexpensive fuel that is politically as well as economically attractive to some of the world’s fastest-growing economies (notably China).

I agree with you completely that developing CCS technology on a commercial scale is a big challenge, and the costs of carbon abatement are high, especially at this early stage before the technology has matured and when the economic cost of carbon is relatiely low.

But I’m not sure in practice that CCS is pushing money away from other technologies like renewables – the EU’s Climate and Energy Package and the Waxman-Markey Bill in the US both seem to treat the two issues quite seperately and if anything are more ambitious on renewables than on CCS.

CCS isn’t a silver bullet – nothing is. But in a few decades’ time, when CCS is cheaper and the cost of carbon higher, we may look back at current (relatively small) investments in CCS R&D and consider it money very well spent.

I’d also add another one: that the use of depleted coal-, oil- and gas – reservoirs as competent storage containers for CO2 is as yet unproven. The pesky gas has a tendency to escape…