The kind of work Ars Digita were doing wasn't algorithmically complex tho' - one template-driven corporate website is much like another. They certainly weren't debugging race conditions or anything mentally exhausting like that. You can just grind this stuff out 12 hours a day if you have to/are being paid enough.
I've done the grind work - used to work in an auto parts plant actually. 12 hour days are exhausting, and your output decreases dramatically after you go past the 8 hour mark. Repeatedly doing this over multiple days results in dramatically reduced productivity.
Read up on the studies yourself - the 40 hour work week was established based on output studies of factory workers - people who, like you say, aren't doing anything complex. They still suffer from performance penalties just like everyone else, and they also eventually go into negative output mode, just like programmers.
Having done the grind work while strapped for cash, I can tell you that the allure of money and the desperation of making rent will only make you productive for so long. Everyone has different limits, but at the end of the day someone who is overworked will likely give up large sums of money just to work less.
As an employer, why can't you give your guys normal 8 hour days? It's more economical for everyone - you are getting sustainable, high output, as opposed to the illusion of working hard, while getting very little out of your employees in reality.
Of course, I would argue that it would come back to bite you in the end. You want clients to send you more billable hours in the future. And that can't happen if you screw stuff up. :-)
But then again, I don't run a successful consulting firm.
In general, you'll hire people who,
* are smart/productive enough to automate the drudgery,
* are smart enough to get by, but whom the drudgery provides some lasting challenge, or
* are screwing around and will likely screw around more as you keep them on for more hours.
So, even assuming that simple work will allow you to get a significant long-term productivity boost working people 8 hours instead of 12, in the long run, you're going to be working with a set of people who'll likely be challenged by the work, so fatigue will cause problems if they're challenged at 8 hours/day, or you could be getting smarter work out of them if they challenged at 12 hours/day.
Of course, building the tools to automate drudgery does take some time, and considering Ars Digita apparently operated during the first .com boom, time-to-market was critical, so some of this logic doesn't apply to the original example.
