I am not advocating this!
I think if you are passionate about your work and work 8 hours a day (5 days a week) at full capacity you are productive enough. I can work more for one or two weeks if necessary (with the adrenalin boost stemming from a near by deadline) but not for much longer.
The first place I'd worked where we launched on schedule with no overtime worked, with all of the features that business wanted for the big 1.0 (well, web-app 1.0... Really just a euphemism here).
My point is that while Arrington goes on about working insane hours, everyone always seems to overlook how much time in the office isn't actually productive for the product. I've been at places where people "worked" 16 hour days, at least 6 of which were spent playing Starcraft LAN games.