The absolute minimum the law allows an employer to pay an employee.
Persons whose work is not worth at least the minimum wage to an employer, are not permitted to have paid employment.
Also prevents employers exploiting workers by paying less than the minimum wage even when their skills are worth more than that - in a economy with significant unemployment, the balance of bargaining power for relatively unskilled workers is otherwise biased towards the employer. In other words, it's a trade off between benefiting some and harming others.
Those who benefit tend to be high technology companies providing automation services while those who are harmed tend to be the poor, the uneducated and the young. See http://www.visa2003.com/visa/work.htm
And so it's up to goverments (and others) to ensure as many people as possible have skills worth at least the minumum wage -- and a great way to do that is to make the MinimumWage equal to zero, as a previous poster stated very insightfully. (by the way, it's not very polite to DisagreeByDeleting). Great if you'd rather err on the side of the people who can afford for you to make a mistake than on the side of those who can't, sure.
(AmericanCulturalAssumption. $5.15/hour as of September 1997. See http://www.dol.gov/dol/esa/public/minwage/chart.htm http://www.visa2003.com/visa/work.htm for a history of changes to this rate.)
In the United States (and other countries?) the de facto minimum wage is the greater of the actual minimum wage, and the amount a person could "earn" by not working from welfare.
Except with recent "welfare reform" acts, it's much harder to stay on welfare than it was before. So welfare does not represent as reliable a wage as it once did. (Whether or not that's a good thing should perhaps be debated elsewhere.)
Not all workers are covered by the minimum wage laws. Some are actually paid much less than they are worth and make up for the difference by generating "tips". The turnover in this type of employment is "very" high.
The minimum wage laws does enforce a certain amount of efficiency on marginal businesses who have business plans that base their success on low wages, part time (less than 40 hour work weeks) which allows escape from provision of certain benefits and privileges, rather than good product and appropriate pricing strategies, You can always tell which firms utilize this strategy - they have an eternal Help Wanted and Applications Accepted signs in big letters on their front windows and doors. You mean like MicroSoft? No I didn't mean Microsoft - but if you mean they are hiring at minimum wage, or part-time, or underpay their employees, and have a big sign on their front door or windows, I'd like to see a picture of that!
Crime is not regulated by the minimum wage law.
Also, a brief bit on TheyMightBeGiants' album "Flood".
(See NamesGivenToComputers to find out why one Wikizen named their computer MinimumWage)