Most of us have accounts at various domain registrars, maybe a couple of parking companies and at least one or two email addressees. With potentially 10 or more accounts, all with different user names, it can be much easier to access accounts by having the same password.
This is a HUGE no-no. If a thief is able to gain access to one of your registrar or parking accounts, he will be able to see what email address is on file for that particular account. Should you use the same password for your email account, he will then be able to break into your email archive. This will allow him to not only change things with whatever account he broke into to get access to your email, but he can also search through your email and see where else you have accounts.
I know that most people use various passwords for different user accounts, and that is smart. I also know than many people are lazy and prefer to use the same password for multiple accounts. Not a good idea.
In fact, someone mentioned this on Namepros the other day, and a three letter .com domain name was stolen from his account. Thieves can be very tricky, and if you have one account compromised, you should ensure that it’s not simple for him to gain access to your other accounts.