This site did not show evidence of storing passwords in plaintext.
This site does allow secured connections (https)
This site did show a clear way to unsubscribe from their emails
This site does verify your email address.
Below is a sample of the emails you can expect to receive when signed up to DrupalCamp.
Thank you for registering at DrupalCamp London. You may now log in by clicking this link or copying and pasting it into your browser:
This link can only be used once to log in and will lead you to a page where you can set your password.
After setting your password, you will be able to log in at https://drupalcamp.london/user in the future.
-- DrupalCamp London team