Ever since the advent of memcached and its ilk, the server-side has been able to benefit from reduced load by caching recently or oft-requested resources. This hasn’t become any less important and valuable. If anything, in this era of the webApp, when native application look and feel is increasingly desired, speedy response to requests is critical for your application to meet the needs of your time-pressed users.
Server-side caching can’t save us from the delay that making a roundtrip from the server imposes, however, and if you’re serving hundreds or thousands of users at the same time, even small memory-cached items may, to the user, seem to be taking their sweet time showing up. For small amounts of oft-requested data that isn’t likely to change often, we can eliminate even these delays by shifting the burden client-side, with local storage and ajax request caching.