How to remove your OpenID account
General remark: the tricky part of logins used on multiple sites is that they mostly all have their own ToS/PP, so removing an open account may not mean removing everything submitted to the sites you used that account for. In those cases it may be really worthwhile to actually read the ToS/PP, for a change.
From their terms: we make good faith efforts to provide you with access to your personal information and either to correct this data if it is inaccurate or to delete such data at your request. So, contact them and request removal: http://openid.net/foundation/contact/ or email@example.com.
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for OpenID using a third-party login such as Facebook or Twitter, you probably want to revoke all access from OpenID. Click here to find out how.