As far as I'm aware from the economics blogosphere, arguments about "structural unemployment" are popular these days mostly in right wing think tanks. And they only seem popular there because hypothesizing that there are tons of jobs available for the unemployed permits one to reject Keynesian/Monetarist prescriptions for further fiscal/monetary stimulus. I haven't run into any serious economist who believes in the i…
I'm not an expert, but I don't think that a structural unemployment explanation is necessarily incompatible with with Keynes. Keynes talks about sticky prices disrupting the classical economic reallocation of resources. This would make sense especially for labour. If you need to go from an 80k job in finance to a 40k job in retail, you would probably be very reluctant and meanwhile be unemployed. That's, to the best of my understanding, a structural explanation.