Imagine that you want to know all inserts, delete's and updates that have been made into an specific table in certain period of time, or because a crash, or because a bad data being processed, so, for these and others situations you can use the triggers to tracking the changes. This can be very helpful to know if there is some malicious user changing things in you database tables.

Have a look at this topic:

http://www.sqlservercentral.com/Forums/Topic1429035-1550-1.aspx

Regards,