Research on free will has taken an interesting turn in recent years. Studies have shown that, when people are encouraged to believe in determinism, they are less likely to behave ethically (for example cheating on tests) and less likely to be nice to others.
The way this is demonstrated is to give participants some text to read – which is either in favour of a determinist view of human nature or in favour of a free will perspective. In one study participants were asked to prepare food for a stranger who disliked hot food. Those participants who read the ‘free will’ text were less likely to make the food spicy whereas those who read the ‘determinist’ text made it hotter. This study and other research is described by Tom Stafford here.
So … this means that, if we want people to behave responsibly, it is important to convince them that they have free will. It doesn’t matter whether or not we do have free will, what matters is that we believe we do.