A great form of slacktavism is changing your facebook picture to support a cause with out actually doing anything that will make a difference. You are one great slacktavist.
The act of participating in obviously pointless activities as an expedient alternative to actually expending effort to fix a problem.
Signing an email petition to stop rampant crime is slacktivism. Want to really make your community safer? Get off your ass and start a neighborhood watch!