A possible strategy for maintaining a verified association might look something like this:
- Gather a reference account from the user, similar to http://soapi.info/findusers.aspx, and upon user selection.
- Gather and verify an email address from your user.
- make it clear that this email address should be the primary email address with which they sign into stackxxxx
- compare the email_hash of the selected User to the MD5 hash of the verified email address (lower cased) and if a match occurs, create the association on your site.
You now have a verified association. You can then use the association_id, if any, of the reference user to get any other accounts the user may have in the stack exchange network.
NOTE: you will soon see an example of this in the samples for Soapi.CSSoapi.CS and Soapi.JS2Soapi.JS2