An very interesting article was posted in c’t about scientific statistics about the decline of tangible activism and demonstrations. The reason for online “slacktivism” seams to be a preference for social visibility and a correlating indulgence user feel when having “done something” when clicking on a “like” button or signing a online-petition. The problem is that real tangible and monetary help falls short with this kind of behavior. Another downside is the high dispersal in online activism as a broad range of services compete for the users attention. Many of whom are not officially recognized by state-officials or suffer from a lack of further political consequences.
To sum up this up … use online petitions to raise awareness but place a strong call to action on traditional means of support with donations, tangible goods and actual physical presence (like demonstrations and actions).
Slacktivism (slactivism or slackervism, a portmanteau of slacker and activism) is a pejorative term for "feel-good" measures in support of an issue or social cause.
Definition from Wikipedia – Slacktivism