This is a classic. From the article:

They're not union members; they're temp workers employed through Allied Forces/Labor Express by the union—United Food and Commercial Workers (UFCW). They're making $6 an hour, with no benefits; it's 104 F, and they're protesting the working conditions inside the new Wal-Mart grocery store.

Is union labor too expensive to use to protest and picket? Does it matter if the people you hire to picket believe in what their picketing for? Apparently not:

But standing with a union-supplied sign on his shoulder that reads, Don't Shop WalMart: Below Area Standards, picketer and former Wal-Mart employee Sal Rivera says about the notorious working conditions of his former big-box employer: "I can't complain. It wasn't bad. They started paying me at $6.75, and after three months I was already getting $7, then I got Employee of the Month, and by the time I left (in less than one year), I was making $8.63 an hour." Rivera worked in maintenance and quit four years ago for personal reasons, he says. He would consider reapplying.

Understanding unions is right up there with understanding airline prices and solving Fermat's equation thingy...