Hello kmblock,
If you are clicking on your own button from your computer it will populate your email address or user ID for logging in just as it may when you go to PayPal.com to access your account, your customer's will not see this, but rather their own information should popoulate to login. If you were to clear your cache and cookies this would render that field blank if you were to go through your own checkout again.
Hope this helps!
JMB
... View more