The gay rights advocacy group Human Rights Campaign (HRC) has launched an effort on Facebook to sway public opinion on same-sex marriage. Can social media activism be quantified and transformed into a significant force in American politics?

Millions of Facebook and Twitter users across the globe changed their user profile pictures last week to a version of the HRC equals sign logo, showing their support for same-sex marriage as the issue was being weighed by the US Supreme Court.

But some question whether viral campaigns on social media will ultimately have any impact in Washington DC.

Produced by the BBC's Matt Danzico