I think it's horrible that the only way to log in is via antisocial networking. It's only one step removed from being a facebook login. If you want it to be discreet, make it anonymous (email address only).
Currently there is only LinkedIn signup available. But we plan an email signup going forward. Mainly we need you to be able to see and select connections, which is easier on LinkedIn. In email it is only possible through a list of emails entered by the user. That's still a good option with some small caveats. Thanks for the feedback.