Let's be honest here: rare is a person who can do cognitively demanding work 8+ hours a day for longer stretches of time. Especially when that's a job, and not one's true life calling.
I also personally find it hard to completely ignore distractions just because of other people - it seems rude to tell them all to stop calling / mailing me during work hours, even though I try so hard.
No one is capable of doing a full 8 hours of cognitively demanding work. I think Cal Newport detailed it out, but the most dedicated and focused people can achieve 6 hours of productive work. Most people can average 4. The 8 hours/day, 40 hour work week is a relic from manufacturing work that has carried over into the office. Between cubicles, open office layouts, meetings, the belief you have to be on premise to be productive, and the execs deluding themselves into thinking they're working the hardest, the US corporate area is not set up for productivity.
I guess a few people misunderstood me. I'm not talking about 100% separation between work and personal life[0], I'm talking about being a programmer, discussing on HN how distractions and interruptions ruins flow - and then running twitter and what not in the workspace. What do I know: some of my habits are weird but works for me but this stuff sounds weird to me :-/
[0]: neither me, my wife nor my boss woukd like that - it's just too practical for my boss that I can make a note when inspiration strikes - outside of work, read work related materials whenever I come across them - even outside of work etc. My boss has stopped caring where I work from and when so as long as I work on my real job (working for a client now) I'll just work from home if my wife wworks night. I and my boss both make sure this is a win-win and my wife has an agreement to call twice or more if she needs to get hold of me before next time I check Telegram.