I believe the GUI is run locally, but if it was run as a web application from the developers site it would only be able to scrape sites accessible to the public internet.
I think it could be easy to do this accidentally. From the main linkedin page, if I save my username and password (which is my email) the linkedin page automatically fills in the login/password box when I revisit the site.
It also has a separate username/password box for giving it access to your email address. I have never used this feature. However when I visit the site it fills in the second box with the same username and password.
If I used the same password for linkedin and my email account, saved my linkedin password, then all I would need to do is accidentally click the wrong button to send them my email credentials.
Isn't comcast also a content provider? They provide cable TV services and own a TV network and a film studio.