While PSA initiatives usually focus on TV and radio ads, a social media component can also help reach their viewership goals. Although a Web site's audience might be smaller than TV's, the viewership is typically more precise.

“You can target your message to blogs that have content in line with your message,” says Chris Cavello, VP of Internet and specialized media at WestGlen Communications. “You're reaching influencers [and] putting [the PSA] into a platform... people are using on a daily basis.”

Blogs are a ...