"But Google is benefiting from this exploitation!" you might say.
Yes. Google can pay less for security services because the guards ultimately cost less. If the guards worked 40 hours/week, the contract cost would have to increase, and another lower cost security company may have won the contract. The reality is that security services are only worth so much. Not every job (even at full time) can or should be expected to pay a livable wage.
The truth is some jobs are simply not worth much to the employer. The minimum wage laws generally are designed to ensure a livable (albeit uncomfortable) income for a single adult working full time. In California, the minimum wage is $8/hr, and scheduled to increase to $10/hr within a couple years. This combined with government assistance programs will generally ensure that individuals with the will to work can afford to live near their livelihood ($500/month room with utilities in the bay area with BART access http://sfbay.craigslist.org/eby/roo/4250779898.html). Of course there are several other factors that impact one's ability to sustain themselves:
Dependants - There is government assistance available for dependant children.
Lack of work - The man from this article does not work full time. The availability of full-time jobs aside, it is not reasonable to expect a livable income on part time, unskilled work.
Major unplanned expenses - Things such as unplanned medical expenses or enormous college tuitions or loan repayments will be a burden to someone making minimum wage.
My point is, 1) I do not accept the assumption that certain jobs are non-livable by definition. For an individual working full time without dependants or edge-case financial burdens, you can generally get by in America. 2) "non-livable" jobs only exist when certain edge case financial hardships arise. In general, assistance is available in these cases, and we have systems in place to support people who fall on hard times. Whether these systems are working as intended is beyond the scope of employee compensation, although there is definitely a case for improving these systems.
There is a third, unspoken point about "non-livable" jobs. People who work these jobs are usually not expected to stay very long. Sometimes these are "stepping-stone" opportunities for the young and inexperienced. Other times these jobs act as a safety net for workers who have lost their higher-paying jobs and need to survive until they can be fully employed. I accept there are people who have no plans or hopes of moving on from these jobs, either due to a lack of marketable skills or even language barriers. I don't believe the answer is in regulating these jobs to pay better. I think the answer lies in educational outreach. Instead of bettering the job, let's try to better the individual so they can get a better job.
Finally, I agree that "someone has to do these things". The market will ensure that the things that need to get done are done. Assuming that everyone "gets better jobs", the supply of unskilled laborers will decrease. From economics, I would guess that a lack of supply for certain menial tasks will have one of two outcomes: the price for the menial task will increase ("non-livable" jobs now become more livable), or a substitute will eliminate the need for the work (automation).
My heart bleeds for these poor, hamstrung corporations.
I'm not sure this is the driver. Instead, the primary factor is likely the fact that hourly employees cost a 50% more the moment they cross 40 hours in a week.
>> Google would rather hire 15 guys at 40-60 hours instead of 40 guys at 20 hours
Not if they are paid hourly, they wouldn't. It would just be throwing money away.
In my way-back days working hourly jobs in retail/fast food/etc., we would game this by trying to get as many excess hours as possible early in the week, so that we could get to 40+ hours by the 5th/6th day. Then, we'd aggressively try to get extra shifts from people who called in sick, etc. But management always tried to prevent this.