Wikipedia:Use of non-free content survey/8

Potential for replacement
Under the current non-free content criteria, non-free content is used only where no free equivalent is available or could be created. This allows important non-free historical photos and commercial properties (e.g. album covers, logos) to be included, but excludes most non-free photographs of living people and technical illustrations as equivalent free photographs and illustrations could be created by Wikipedians.

In my opinion, the requirement that non-free content not be "replaceable" is: