These are Facebook’s memes. The share button, in its current iteration, allows users to take content from another user’s profile and re-post it on their own profiles, along with a byline from the original poster. By design, it works like Tumblr’s reblog or Twitter’s retweet functions. In practice, it can work more like a human centipede.

https://www.buzzfeednews.com/article/jackstuef/the-dark-side-of-facebook-memes