Concurrent updates
Clemens Vasters: The "create" story of REST using HTTP PUT is very pretty for this and HTTP GET speaks for itself. It all falls apart when you think about concurrent updates and concurrent deletes. These simply can't exist in such a world. As long as you only create stuff and reference stuff, all is fine.
Obviously, Clemens hasn't heard about the expires header. All you have to do is predict with 100% accuracy when the next POST or DELETE request is going to come in, and all caches will remain perfectly in synch.
It is just a SMOP.