Laws in Europe and the US make it clear that a service provider only becomes liable for the illegality of user-generated content if it is informed of law-breaking material and refuses to remove it.
The Brazilian court ruling finds Google responsible for the original posting of the material, according to reports.
Agence France Presse (AFP) said that Brazil's O Globo daily newspaper reports judge Alvimar de Avila as saying that Google is responsible.
"By making space available on virtual networking sites, in which users can post any type of message without any checks beforehand, with offensive and injurious content, and, in many cases, of unknown origin, [Google] assumes the risk of causing damage [to other people]," the judge said, according to the report.
The comments concerned an un-named priest who was called a paedophile and a thief with a lover in a posting on Orkut. The priest sued in 2008 and won his case. The recent ruling backs that lower court's decision.
Google was fined $8,500 in the case, the report said. The comment was made anonymously.