This is smart politics. Rather than simply telling people FB is a monopoly, she runs a limited experiment that had it been left alone, would have limited effect since the budget was so small ($100). Now this puts FB in a bind. If they really are a middleman for content, then these ads don't violate any laws and shouldn't be blocked. However, FB as a company with a product should block it just like coffee shop wouldn'…
Are there any examples of such "neutral platforms" outside of web company marketing?
Was this term coined by web companies?
Seems to me like a more concrete term to describe a web company such as Facebook is "MITM". This has a specific meaning and we can all understand how it applies. A MITM could be benevolent, malicious or perhaps "neutral". (The existence of the later might be obviated by peer-to-peer connections.)
If there could be such a thing as a "neutral platform", then maybe "the internet" is the best candidate. Not any particular MITM, whether benevolent, malicious or "neutral".