Can I cancel/delete my SSO account?
Yes, but if you use any other services through login.ubuntu.com, you should delete those first -- especially if you have any paid accounts. Examples include Launchpad.net, AskUbuntu, and anything else which uses the Ubuntu Single Sign-on service. The SSO support team cannot delete those other accounts for you, but most of them have self-service options.
To see which sites you will lose access to and should delete first, log in to your SSO account at https://login.ubuntu.com/ . It should show a list of other sites you have recently logged into via SSO. If you delete your account, you will lose access to all of those sites too.
To delete your account, you need to go to https://login.ubuntu.com/+delete and follow the instructions you'll find there.
Please read such instructions carefully before proceeding to the deletion of your account, as you'll permanently lose access to your information.