@evan BaaS systems have a server, but it is just a very generic server, so most of the functionality and logic gets pushed down the client. That's the sort of model that I'm seeing.
Re: Webfinger. What they wanted was a concept of "follow your nose" and, originally, there appear to have been two camps around webfinger:
1. Account IDs should be a dereferencable _http_ URI.
2. Account IDs can be acct: schema so long as the other side knows how to process that and connect with webfinger.