With zabbix_server running, if mysql user "zabbix" privileges or password change, drop, or are somehow affected, zabbix_server dies silently.
It should still email to user group set in "User group for database down message" under "Administration --> General --> Other"
How to reproduce:
With zabbix_server running, connect to mysql, and change password for 'zabbix' user:
mysql>update mysql.user set Password=password('anydifferentpassword') WHERE User='zabbix';
25085:20100108:185838.859 [Z3001] Connection to database 'zabbix' failed:  Access denied for user 'zabbix'@'localhost' (using password: YES)
25085:20100108:185838.869 One child process died (PID:25118). Exiting ...
And no email to zabbix administrators sadly.