SVN talk about the programming zone. Everyone's had it - getting an idea at 10pm and working on it till 2am; hitting a sweet spot and coding till your eyes bleed; managing to block everything else out and go on a blitz....
The office environment is not conducive to this. It would be interesting to see exactly how 37 Signals work - they're clearly not a typical company. How do they have company meetings? How do they collaberate with such a loose environment?