System hardware requirements
Just some random observation: At LinuxTag a surprisingly frequent question was “what are the hardware requirements for BSD?”.
From my perspective this question is really meaningless in regard to PCs/general purpose hardware (even though I do understand the wish to reduce things to simple numbers and statements). The “hard” system requirements, the ressources you absolutely need to get things running, are so low that they can be taken for granted nowadays.
Just to have a good answer we checked the NetBSD/x86 documentation and it states that a minimal configuration should have an i486 CPU with 4M of RAM and 40M of disk space. So IMHO the notion of a “hard” requirement only applies to the embedded world (have a CPU without MMU? or less than 2M of RAM? – Not enough for BSD or any other modern Unix.)
What remains are “soft” system requirements or performance requirements, the ressources you need for a given performance target. For example “I want to use the KDE desktop with all plugins and graphic effects”, “the mail relay has to process X messages per hour”, or “the router has to handle a bandwidth with Y amount of data and Z packets per second”.
These are no trivial questions because they require benchmarks and they may have multiple answers (e.g. with different trade-offs). Their answers may be very important for a systems architecture or a business decision… But these are not the questions that decide whether I take a Live CD and try it out on my PC at home.