I really do wish HTTP had a mechanism for responding to a single request with multiple combined response bodies as if requests were made for each individually (from the perspective of, e.g., a caching proxy) - the loss of separation of concerns from merging children into the parent isn't just a usability issue, it also means you lose your cache granularity - the cache for the parent object is now stale whenever a child is modified, and a request for a child after getting the parent won't hit the cache at the request level.

There's keep-alive, but that still means that if you want to get a parent and its children, you have to wait for the parent request round-trip.

To add - this is a major issue we've been working through at Slant.co - we've combined child objects into the requests for the parent objects (sometimes even two levels down), but it's significantly complicated caching efforts - we're in the process of building some namespacing into our server-side request cache, so we can transparently make cached Question and Option pages stale whenever, e.g., the title of a Pro/Con gets changed. If HTTP allowed multiple responses, we could treat everything transparently server-side as individual requests, and get much higher hit-rates for proxy and client-side caches.