Its physical appearance contains many cues to suggest its reliability. As a carefully bound, handsomely produced book that has hundreds of pages, it is recognized as a commercial object that clearly required a large research staff and capital-intensive corporation to write, print and distribute. It is printed in huge quantities and sold on the national market by a well-known book publisher. All of these facts, implicit in the physicality of a dictionary, help persuade that its contents are rigorous and trustworthy. Such contextual cues impute meaning to the contents of physical documents.
Digital documents are different.
They are shorn of such implicit context, or perhaps more accurately, that context may not yet have been socially established. Hence the stature and credibility of a given digital document are often culturally or socially ambiguous. All the contextual cues that were once implicit in the physical embodiment of a document now have to be explicitly supplied or inferred. The provenance of e-mail, for example, and other digital documents is uncertain, and their ultimate destination, readership, or even authenticity may not be controllable or predictable with any certainty. When documents are no longer instantiated in a particular physical form that has a recognized social significance, it can become more difficult to ascribe larger meanings to a given collection of words.