brucelawson

There are many sites displaying song lyrics or poetry. In these artistic works, line breaks are important; they carry meaning. 
Most sites markup the authorial line break with a <br> element to force the browser to honour the author's intention.
However, there are many occasions when a narrow screen forces a long line to wrap, and it is not possible for the reader to determine which line breaks are authorial (and thus have meaning/ semantics) and which are added by the browser (and are thus presentational).

In printed media, there are typographic conventions to indicate the difference.

brucelawson

China https://en.wikipedia.org/wiki/List_of_websites_blocked_in_China 

Pakistan https://en.wikipedia.org/wiki/Internet_censorship_in_Pakistan, https://www.usenix.org/conference/foci13/workshop-program/presentation/nabi 

Russia http://eais.rkn.gov.ru, https://en.wikipedia.org/wiki/Russian_Internet_blacklist

Turkey http://engelliweb.com, you can check any website from gov. website (eekg.tib.gov.tr)

UK https://en.wikipedia.org/wiki/Websites_blocked_in_the_United_Kingdom

brucelawson

[My initial list:]

DRM
speed for superhi-perf games
app store placement
source-code secrecy

[list compiled from other people's twitter answers; thanks all!]

pushing native notifications when they're not in the "app" (several people said this)