[johannes1234321]

> In practice, however, few people worry about reasonable amounts web-surfing, being on hacker-news or doing life-activities on their work machines. Oh, here I am on hacker-news when I should be working.

This is all nice and good, till the employer needs a reason to fire an employee, then suddenly all such things become relevant. Maybe a bit less in at-will employment situations where there are low barriers for kicking people anyways.