Full Idea
Heidegger came to say that the cultural mood had changed from 'anxiety' to 'boredom'. The danger is that our boredom has become so ubiquitous and all-encompassing that it is now hidden.
Gist of Idea
Culture is now dominated by boredom, so universal it is unnoticed
Source
report of Martin Heidegger (Contributions to Philosophy [1938]) by Kevin Aho - Existentialism: an introduction 9 'Conc'
Book Reference
Aho,Kevin: 'Existentialism: an introduction' [Polity 2014], p.164
A Reaction
I'm not sure what the danger of boredom is if it is 'hidden'. It rather depends what else is hidden with it.