"Well, HTTP/1.1 pipelining is another attempt, but one that's almost entirely failed in reality due to both its deficiencies (replies have to be in order, etc) and all the broken proxies (transparent and otherwise) that lie and say they're HTTP/1.1 but actually fuck up pipelining. So in practice clients don't use it, because it's not safe. Great thing about SPDY and forced SSL is there it's hard to have any broken transparent proxies! :)"
- Brad Fitzpatrick