This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
If you have to ask, it probably isn't needed in your application. Seriously, warnings aren't looked at in most business applications. The first example that comes to mind is an application that troubleshoots database connections.