foaf:mbox_sha1sum. Many FOAF producers, such as LiveJournal put
foaf:mbox_sha1sumin their FOAF. Nice!
Unfortunately, Flickr does not support FOAF. OK, no big deal. I made FOAF wrappers for Flickr people profiles. However, if I am not a contact of that user (which for 99.99% of Flickr users, I am not) I can't see their email addresses. This is a great idea, I'm glad they don't publish it to everyone. Except even in the Flickr APIs there's no way to get the email as a sha1 sum.
I sent the Flickr API mailing list a note asking them to add this. How can I make a stronger case? They don't even need to adopt RDF or FOAF here. Just put in a sha1 hash of the user's email address in the response to the call flickr.people.getInfo.
That would be amazing if they did, and smushing all these FOAF profiles would become possible.
Advice on how to make the case?
 To combine RDF triples so that duplicate nodes are removed and similar objects are consolidated.