One of the best examples of the semantic web was Daylife[1], and they wound up being "acquired" by two bit players[2] that figured out how to monetize things better.. :-/
[1] https://en.wikipedia.org/wiki/Daylife
[2] https://techcrunch.com/2012/10/17/content-licensing-service-...
I made a few observations in my own comment.
One being that there is no usable graph store you and I can use as of 2018.
Another being about monetizing the Semantic Web when playing the role of the data/ontology provider. You provide all the data while the consumers (Siri, Alexa and Google Home) get the glory: https://news.ycombinator.com/item?id=18036041