With all systems that require passwords and all sites that require an account to access is not possible to remember all the usernames and passwords without good combination using the same credentials or write them all. There is a huge security problem by doing one of the two options.
For people who use the same credentials for everything from their webmail account to their personal bank accounts for them to leave themselves open for someone to have full access to their lives. You can find best password manager and password management software from various web sources.
All it takes is for someone to get an account, and they will have access to one of the accounts. Gaining access to initial information obtained from cookies stored on the machine to websites fail to use https: or SSL (secure socket layer) technology. This sends your username and password credentials in the clear on the Internet and has the possibility of being picked up by a number of machines.
By writing the username and password combination on a piece of paper, there is always a good possibility of losing a piece of paper or of someone actually found it and has direct access to the account.
This threat is greater when the pieces of paper left in the bottom of the keyboard, taped to the monitor, recorded on a laptop, or just left on the table. the password used to add security to computers and applications, by writing the information that people just throw away security.
One of the best things to do when setting up an account is to use a different user name and a different password for each account during the initial setup. It can be tedious and difficult to remember (thus, the two tendencies referred to above).