The World Wide Web and grid computing provide new opportunities and challenges for artificial intelligence. This talk examines how case-based reasoning can respond to these challenges by leveraging large-scale information sources. It highlights opportunities for exploiting naturally arising cases and augmenting them with additional open sources, to enable robust support for human reasoning. It illustrates with examples from current research, focusing especially on how CBR can leverage frameworks being developed in burgeoning research activity in provenance capture and storage.