Require Unique Custom User Profile Field
 

I would appreciate the ability to require a unique value when creating a custom user profile field (for example, if you were using a custom user profile field to store a "display name", you would want each user to have a unique "display name").

Does anyone have any ideas?

Did you ever find this? I too would like to be able to make a custom profile field unique.

in the custom field, (userfields) impossible... but you can require a hack that will add a new entry in the user table that can verify the content of the field and make sure it is unique... so you can attach that feature to a function to let members enter their content, and the function to display it where you want.