Sure, but that means I have to either run a memcached instance on every server (which I've actually had to do before just for the sake of PHP) or I have to make

Sure, but that means I have to either run a memcached instance on every server (which I've actually had to do before just for the sake of PHP) or I have to make network calls for something I shouldn't have to, and then also do serialization/deserialization. That's fine for plenty of things, but certainly isn't optimal for all sorts of stuff. Not to mention, all the other languages out there memcached just as well.