Feed aggregation is used to index frequently updated content such as blogs, news, podcasts, forums, ect... A feed can contain either a summary of the content and/or the full text. The ablility to pull content from multiple sources and store them in one place gives you an advantage.
Part of the Social Search Engine involves RSS feeds. Users can submit their favorite feeds to be aggregated by the system. The latest news will be categorized and indexed, keeping your users in touch with the latest information.