Americans eat in restaurants more often than any other society yet most of us don't know the people who prepare and serve the food there.  And, also in America, we are taught the custom of tipping, but the problem is that it isn't a tip per se, it is that person's salary that we are paying.  There is a separate minimum wage for tip earning people and it is 2.13 per hour.  Most restaurant workers are paid the minimum wage.  If the customer doesn't pay the 15 to 2-% tip, that waiter is working for free.  Actually it is even worse than that because the waiter is expected to pay the bartender and table runners whether you pay your tip or not.  If the patron walks out without paying their bill at all, the restaurant manager holds the waiter responsible for it... often times the manager will require the waiter to pay the scofflaws bill (although it is technically illegal to hold a third party responsible for someone else's debt, it is done all the time.)
For the same reason, waiters must tolerate verbal abuse and sexual battery from customers.  If a waiter does not tolerate the intolerable, then the waiter knows he/she will not get paid.  

Furthermore, this is an industry where the employees are largely not given paid sick days.  Restaurant workers are among the lowest paid people in the American economy.  This means that the person who prepares or serves your food is incentivized to come to work sick.

According to Saru Jayarman (who wrote the book Behind the Kitchen Door) we can't really have sustainably sourced food without also creating sustainably sourced wages for restaurant workers.  Check out this message from the Unitarian Universalist Society of America.

Come join us next week.  Every week is a presentation on something different, but each one will be based on our seven principles.  Oh, and we generally also have a discussion afterward, but we serve coffee, juice and snacks with that.