The so-called "young invincibles" are so important to the success of the Affordable Care Act that supporters and detractors are spending millions to reach them with racy ads, social media campaigns and celebrity endorsements. The president is even (gasp) asking their mothers to help convince them to sign up for insurance. The federal government and states running their own exchanges have launched marketing efforts for this crucial demographic of healthy young adults, but it's unclear if the messages are getting through. Eric Fisher, a 28-year-old from Salt Lake City, said he still hasn't seen any of the social media campaigns — one of which targets Utah residents with images of people snowboarding and rock climbing.