[url=http://martinfowler.com/bliki/ObservedRequirement.html]Martin Fowler[/url] suggests to gather (new) requirements by analyzing user behavior within the application/web site.
[quote]Everyone knows how big the difference is between what people say they want and what people actually need and use. By watching what people actually do with your application, you can find out what actually happens with the software – which can give you much more direct information than other sources. As a result I think more teams should consider adding this approach to their toolkit.[/quote]