Yes, I understand your concern. But your data is completely secure with us. Your password is encrypted with security algorythm. We never display your password with anyone, not even you. If you forget your login details, we'll mail it to your registered email address. (the one used during registration, requires manual verification by our team to change this address).
You can provide your wordpressinstaller.net account information with your writers/staff too as they can't do anything major except posting to your blog.
And still if you don't want to use any blog management feature, you can change your blog and control panel's password after installation.