Quantative easing is used and works if done in tight boundaries, as with anything you can have too much of a good thing. Doing it on the scale he suggests is clearly foolhardy to anyone without left wing rose tinted spectacles (and I think some of those are even surprised at his suggestions).
I do think the Government could be doing more though. Building infrastructure is a sound investment, so long as it is controlled, but the Government just dont seem interested in, say house building or prison building which I think would go down very well with the majority. It's not as if it has to be all public money after all.