Jihadists have even used hashtags like #Hawaii and #Ferguson to capitalize on attention being paid to US news stories.
"Terrorism by its very definition is a communications strategy," said Max Abrahms, a political science professor at Northeastern University. "In a way... use of social media shouldn't be that surprising because this is 2014 and everyone uses Twitter."
But he said IS had demonstrated a mastery of social media that far exceeded that of groups like Al-Qaeda. That strength is partly a result of the growth of social media in recent years but also the work of the young and often Western-educated recruits who join IS.
"These Westerners have a leg up in terms of exposure to social media and frankly their English skills are much better for reaching out," he said.
For IS, which grew out of the ashes of Al-Qaeda's former Iraqi affiliate, grisly postings on social media have become a way to "project strength" and attract recruits, Abrahms said.
"It repels most people in the international community, but does have some appeal among already radicalized segments."
Jihadist use of social media platforms has not gone unnoticed by administrators, and Twitter had begun suspending accounts of some extremists even before the Foley video was published. After it was released, Twitter CEO Dick Costolo announced that the company would suspend accounts posting graphic images from the video.
YouTube also quickly removed the video for violating its terms of usage, though it remained online on other sites. Twitter users themselves sought to stop the spread of images from the video, using the hashtag #ISISmediablackout to urge people to avoid giving the group publicity.
"I won't share any photo or video of violence intentionally recorded and released by ISIS for propaganda," wrote user Hend under the name Libya Liberty. "Amputate their reach. Pour water on their flame," she added.
But it remains unclear how effective such attempts will be. By Wednesday afternoon, several suspended Twitter users were back online under different names.
"New account LOL spread the word. 'These terrorists keep coming back,'" one user wrote.