I have the feeling that some of the people commenting here do not remember HTTP 1.1 first emerging and some of the interesting consequences that came with it for both site operators and browser users.
Sure, it was a very different time, when most people who had sites were generally more tech-savvy than most of today's site owners (speaking as someone who's done support for off-the-shelf site running software)... but an awful lot of sites had a slightly ugly transition.
If I remember rightly a lot of it came down to the simple Host header which wasn't required in 1.0, mandatory in 1.1 to allow name-based virtual hosting to work (1.0 assumed one site per IP address, something that clearly doesn't work in a shared hosting environment) but that broke a lot of things in the middle, especially proxy servers. Sure, now, it's not a problem because most things are using 1.1 but it's interesting to note that there's still a fairly large undercurrent of things not implementing 1.1 for various reasons.
I haven't read the 2.0 spec, mostly because these things seem to change almost like the wind (like some of the stuff in HTML5 at times) so once it's moved on a bit I'll check it out and see if the firewalling systems I work with will need any changes (given that they do a little behavioural profiling based on what a given set of HTTP headers they see containing... there's going to be changes needed), but it's probably going to be 2016 before I really have to worry about any of that.