Snapchat, Instagram and Pinterest arrived on the social scene after Facebook and Twitter, but they quickly made their marks, especially among millennials. After reaching critical mass, the three companies are attempting to monetize their services by rolling out new features for advertisers. Select large, global brands, including McDonald's, are testing the new features and could be role models for other marketers interested in the apps. However, all three services are still relatively young, and it might be too early to tell if ad campaigns are worth the investment.