In the past, cracking passwords or finding other holes to get into a computer system required a significant time investment on the part of a hacker. Due to the increase in the speed of modern computers there are now personal computers that can do the job in hours. There has also been a significant increase in the number of tools available to a hacker. It is no longer a realm limited to only the dedicated hacker.
Most tools are readily available off from the Web, and require little to no knowledge to use.
A good password is important both to protect your own documents and to protect other accounts on the computers that you log in to. Even if you feel that you personally do not have any files that a hacker might be interested in, once that they are in through your account there is a greater chance that they will find some way to access other accounts. A good password is one that can not be guessed by others or easily determined by computer dictionary attacks. Using longer passwords, mixed-case, digits, and punctuation is highly recommended if the system permits it. A bad password is one that can be guessed by others.