This refers to "The Grapes of Wrath", published in 1939 by John Steinbeck.
In the context, California fruit and vegetable growers would attach these handbills all around the Dust Bowl. This meant that they ended up attracting more workers than actually needed, consequently plundering wages down to starvation levels. Even though it was an opportunity of work, the conditions were really grim, meaning that without knowing the full picture, they could have been excited, but it was really short-sighted and would not really justify in the end.