What happens when a deadline is missed?

This depends on your workflow definition. In the simplest case an e-mail is sent to another user by the system (typically your supervisor so watch out!). However in more sophisticated scenarios a missed deadline can redirect that path that the workflow takes. One customer uses deadlines to automatically make an approval if the deadline is missed (at about the eighth approval level!!!). This gives the user the chance to make rejections but does not force him/her to go into the system to approve the other 99.9% of the requests. In safety critical environments the workflow might trigger off preventative action when a deadline is missed or might put other processes on hold. There is no limit as to how you can use this functionality.