Robert Koch's Masters Thesis about websockets security and adoption is linked.
interesting tidbit - he surveyed 15K free apps from the google play
store and saw only 14 that use websockets. Previous surveys of traditional websites have seen similarly poor uptake.
WS certainly isn't optimal,
but it has a few pretty interesting properties and its sad to see it underused. I suspect its reliance on a different server and infrastructure stack is part of the reason.