An online repository of directory listings. If ever there was something well suited for the online channel it is web-based phone directories. Databasing (primarily) public data would seem to be the sort of simple task ideally suited for the web. Even if it weren't public date it should still be an easy mark. The internet, after all, is the most efficient means ever invented for getting your hands on information your aren't supposed to have.
Our inability to predicted to uses and effects of technology should never be underestimated, especially when it comes to the internet.
From the Foundation archives: Technology and Culture: The foreseen and the unforeseen