I already mentioned this in another comment, but it&#x27;s also relevant here: I don&#x27;t understand why it&#x27;s assumed that contact and identity isolation should lie at the service provider boundary.<p>People are able to manage multiple email addresses and phone numbers for work&#x2F;personal&#x2F;whatever without too many problems, and despite being against Facebook&#x27;s terms of service many individuals already create more than one Facebook account to keep stuff separate (&quot;I don&#x27;t want my boss to see photos from that party last weekend&quot;). In a standardized IM interop utopia I&#x27;d imagine that juggling multiple identities would be even more common.