only-work-on-one-thing
From here: https://news.ycombinator.com/item?id=8636436 about context switching it talks about Spolsky's post:
http://www.joelonsoftware.com/articles/fog0000000022.html
"The real lesson from all this is that you should never let people work on more than one thing at once. Make sure they know what it is. Good managers see their responsibility as removing obstacles so that people can focus on one thing and really get it done. When emergencies come up, think about whether you can handle it yourself before you delegate it to a programmer who is deeply submersed in a project.
In one podcast (I can't remember which, but I'm feeling the Tim Ferriss Show) the guy mentioned that Peter Thiel made sure that people were only ever working on one thing at a time so he would ensure that the thing got done.