or so suggests this article:

http://www.economist.com/node/18587506

Unfortunately the logic isn't really teased out fully:

"The labels need HMV to survive in order to keep lucrative non-chart music on the high street. So too do the independents, for if HMV were to fail, the labels would cut back their operations, drastically shrinking the market."

Does the existence of a substantive CD market require at least one major 'music' retailer to survive, at least in physical store form?