If you are into programming and work with large code bases, then too large amounts of ram would be quite useful. Especially, the linking phase uses a hell lot of memory. Large code bases would easily max out the physical memory and result in a lot of disk trashing not to mention extremely long build times. Higher amount of RAM reduces this time drastically. At my previous company, the code base we worked on used to take up 20~30 min just for the linking phase alone with 2GB RAM in the system. The same happens in 1 min with 8GB RAM.
If you work with or intend to work with open source code base's like Mozilla or Chromium, some of the build options require 8GB+ RAM.
Other than that, if you have interest in trying out various Operating systems, you can setup Virtual Box VM's and run your OS from there. Given enough RAM, you can run the OS full screen and high resolutions and you would never feel that you are running a VM.