With the different types of attacks on the internet, a dictionary attacked ran by an automated script can be the most dangerous. Often I check our logs on many of our outside honeypots and ftp servers only to see 13 megabyte log files that show a script that ran for several hours. The account that is tried the most is the administrator account. Continuously throughout the script, I will see the Administrator username and thousands of entries for different passwords from a dictionary attack.
These servers have been protected by renaming the administrator account. By renaming the account, a dictionary attack becomes useless if the correct username cannot be guessed. Many reviews argue against this point saying that it is superfluous. (This meaning seems to be taking hold in the IT industry and simply means unnecessary).
The theory behind this (being flawed) is that an attacker would get an error message and if the password was complex enough that renaming the account isn't needed. Now think of it this way, if you had two locks on your door would you leave one key in the door? Faster speed broadband connections and more complex programs allow attacks to be accelerated. Simple and Complex programs can be found on the internet to run scripts or to design hacking programs. Why wouldn't you take this extra step?