The authors recognized a close similarity between practices used in online genealogy research and those common in online education. Uses of a popular online database service were examined within a peer instruction community dedicated to researching a family history topic. Three community subgroups were divided into leaders, who base their work on external sources, and followers who copy the leaders' conclusions. The accuracy and error levels of the 21 family trees produced by these researchers were calculated in relation to data obtained from offline archives. The trees created in the online process all contained flawed details and invalid conclusions due to practices similar to those of massive open online courses. The inconsistent reliability of the online approaches is discussed in terms of the "fog" that descends upon knowledge when facts are distorted by academic jargon, disciplinary trends, and institutional priorities, and which increases with its transmission to others by non-experts.