Can customers continue to use the content Sony is removing from their accounts, if they have previously downloaded it? I assume that "buy" doesn't require the vendor to continuously maintain the content on their servers, to be available for free download, forever.

Of course, customers would also need a way to transfer the content from their existing devices to later-purchased devices. If that is possible now, but becomes impossible later (like if Sony goes bankrupt), then does that ruin the "buy" characterization that seemed legit at the beginning?