Login twice on same account? Good or potential security risk?

I don't really like the idea of it. I always thought my characters would be safe as long as I'm logged on but if someone was able to get access to my somehow, I can't really stop them from logging on my account as well... :/ Sure it has advantages but I don't think it's worth the risk.

I'll just play two accounts on two computers if I want to give CPQ wins xD