So, I was letting someone I know use my account so he could publish a map on SC2(He plays on the SEA servers, I'm on US), and once he tried to log in it instantly put the account(The Bnet account, not just SC2 account) on lockdown until I went into my email and changed the password.
Pretty fancy, but I can see how it could have some drawbacks. Namely going to another country and getting locked out.