If you are running a business that uses a multitude of different programs that all require users to create and use a new username and password for each application, you are likely to find that your staff is wasting an inordinate amount of time trying to remember all of the various usernames and passwords and then the time needed to log into them all. Single sign on authentication can reduce this wasted time significantly.
Links:
[1] http://www2.digi-sign.com/node/3743