Starting last weekend, I rather belatedly began blocking HTTP/1.0 (actually, everything that wasn't 1.1).
Most of the blocks I'm seeing due to this are valid and would in any case have been caught by other means. Those that are not valid catches seem to be proxies, especially for UK education (mainly schools). Annoying because at least one of my sites is used by schools. Some (but not all) of the proxies also have faulty header field combinations, for which I'd previously had to make exceptions. I've now had to add HTTP/1.0 to the exceptions for these. Doubly annoying because these were the teachers I was trapping but pupils use the same proxies in some cases and I'm concerned about them abusing the loopholes. Ah, well.