emails are unique acorss the systems whereas $$USER.name may not be.
Also, since name may include umlauts/accents that variable is not ideal.
I want to filter (report/view) based on the current user's email address because on our case the address is stored in custom field when we don't find the user; if the user later were added to WF I'd like to have a report to show those items where the custom field has their email address
