In France, "95 percent of people who have received a first-time notice of illegal sharing 'do not give rise to the need for a second notice,' that 92 percent of people who received a second notice cease illegal sharing, and that 98 percent of people who receive a third notice 'show the same trend.'" http://www.theverge.com/2012/9/11/3316158/graduated-piracy-r...

So yeah, telling people "don't get caught again" works.