Professor Eric Goldman noted an interesting case in California involving the alteration of content and the applicability of the CDA's §230 immunity.  Section 230 provides:

No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.

The case at hand, Hardin v. PDX, a California case, involves a software manufacturer, PDX, who allegedly "truncates" the information associated with a software program that transmits drug prescription information.  On the one hand, as a mere intermediary of the information, PDX would appear to qualify for §230 immunity.  However, since PDX designed its software so that the prescription information could be altered to omit warnings, the California courts found no immunity applied under §230.  Professor Goldman joined with five other law professors in urging the California Supreme Court to review the case.  

You can read Professor Goldman's post on the case here.