Do you remember every online account you've ever made? Most people create dozens of accounts that they have only used once. Just think of how many times you've created a username and password just to read an article, play a game or download something.
That's actually very dangerous. It means your information is floating around on dozens or hundreds of websites that may or may not be secure.
Even worse, if you used the same username and password for every site, then every account you have is in danger. A hacker who gets your account from one site can get access to your other accounts.
That's why I hunt down and close any accounts I'm not using, and you should, too. How can you possibly find them all? Well, there's a simple browser trick you can use.