The Internet horror creation, and modern urban legend, emerged on the Something Awful forum, and is the most famous of the creepypasta stories out there. Although created by Eric Knudsen, aka "Victor Surge," Slender Man has many roots in folklore and pop culture (See: The Gentlemen from Buffy the Vampire Slayer, and The Silence from Doctor Who).
While there is more news to come, Screen Gems has a strong track record of success with its previous films The Mothman Prophecies, Boogeyman, The Exorcism of Emily Rose, Hostel, and the Resident Evil and Underworld franchises.
Read more about the paranormal roots of Slender Man, and let us know if you think a Slender Man movies sounds like your kind of horror -- or if it doesn't work outside of the Internet.
-Aaron Sagers