I dont know why more web servers are not using UDP by default and only go TCP when the client or content needs it. For example, sites like youtube - the videos must be streamed to us, why not the site itself? Only when I want the client to definitley know it sent data (a banking transaction, an amazon order) but for the vast majority of sites UDP bi-di should be fine.

Can you imagine the amount of bandwidth saved around the world in aggregate?

TCP should be restricted based on content classification.