Further Edit: You may be interested to learn that this post is one of the most frequently viewed pages on this site. Whether that’s a reflection on the readership of this blog, or just to the internet as a whole, is impossible to determine.
Edit: The case referred to has now been posted at AustLII, as Hayes v Surfers Paradise Rock and Roll Cafe  QDC 214.
I can’t find the case itself, but the article in a Queensland online paper contains enough detail that it might be genuine.
According to the story, a magistrate searching for the definition of lap dance in a licensing matter sought assistance from secondary sources. When the Oxford dictionary proved no help, he obtained a definition on-line. On appeal, the District Court is said to have ruled that the magistrate was wrong to rely upon the definition without allowing the parties to make submissions on the point
It wasn’t that the source was considered inherently unreliable, though. “The failure to permit the parties any opportunity … with respect to the Wiktionary entry as to the meaning of ‘lap dance’ must be seen as a denial of natural justice,” Newton J reportedly said.