Why is this necessary?

In order to protect your account from numerous attempts to guess the password, we're blocking it after five unsuccessful login attempts.

If that happens, the following message will appear on the screen:

Too many unsuccessful login attempts! Your account has been temporarily deactivated.

How can I reactivate it?

Your account will be automatically reactivated in 15 minutes.

You can reactivate it immediately by clicking the link in the email sent to the associated email address.