From Turabian 8th Edition: http://www.press.uchicago.edu/books/turabian/turabian_citationguide.html
Comment posted on a social networking service
Cite in running text (“In a message posted to her Twitter account on August 25, 2011, . . .”) instead of in a note, and they are rarely listed in a bibliography. The following example shows the more formal version of a note.
Blog entry or comment
Cite in running text (“In a comment posted to The Becker-Posner Blog on February 16, 2012, . . .”) instead of in a note, and they are commonly omitted from a bibliography. The following examples show the more formal versions of the citations.
Becker, Gary. “Is Capitalism in Crisis?” The Becker-Posner Blog, February 12, 2012. Accessed February 16, 2012. http://www.becker-posner-blog.com/2012/02/is-capitalism-in-crisis-becker.html.