Changes in the information society, especially the rise of blogs, have refocused attention on
questions of media modality, source identification, and motivation in online environments.
We manipulate the structure of a blogger’s critique on a news story (global vs. interspersed)
and the partisan target of the blogger (Democrats vs. Republicans) in an experiment
embedded in an online survey. Our results support our expectations: The more difficult
story format decreases the ability of less motivated readers to correctly identify the source
of their information, without affecting the motivated. These effects of structure on source
identification are democratically consequential when people rely on blogs for facts about
public affairs without the proper cautionary caveats regarding the credibility of the source.