heres a funny example i just thought of:
you are production support for web application pointed to by
www.jesusangeles.com. it had some problems so you shut down the web application, while you debug it. but you gotta sleep.
so you tell the sys ad, 'whatever you do, dont start the application, i am still fixing it'
but you dont trust him, so you use ServletContextListener so that when the application is started, it will send your cellphone a message 'app is upped'.
and so you slept, and it happened. you called the sys ad and told him to shut it down.
you also made the ServletContextListener to send you a message when the application is shut down, and you will get a message 'app is downed'
then you get that 'app is downed' message, and tell the sys ad, 'please dont do that again, i am trying to get some sleep here'