But there were servers that thought they supported pipelining and had corruption issues, so the clients got scared and wouldn't use it. (Besides, the modems on the edge of the web were the problem, not the latency.) Then the proxy people said "Why bother? No one uses it.", and the clients continued to not implement it, or did but left it off by default with a switch to turn it on in a disused lavatory, behind the "Beware of the Leopard" sign. Meanwhile, the server people having run out of useful and useless features to add to their vast code bases actually got around to making pipelining work correctly.
Welcome to 2010.
• Most popular web servers support pipelining, probably correctly.
• <1% of browsers will try it.
• Proxies (firewall and caching) largely break it.
• If you are using scripts that can change the state of the web server, then your head might explode when you consider what happens with pipelined requests.