As I've now read over the current notes on Activity Streams and Activity stream verbs - I'd like to point out other 'verbs' which aren't covered in your current notes and which wiould be prime for "inter-connecting" between social networks. I assume this is something the DiSO project would be interested in.
DiSO should be able to be used by other social networks - to gateway their user's profile data, social graphs and content to any DiSO enabled social network. IMHO.
The following verbs are about interoperability, not dataportability.
Send a Message - it would be nice to be able to have one of those private social network 'InBox messages' systems - send messages to InBoxes in otehr systems. These Messages would only be allowed through pre-tunneled 'access' rights, but if a facebook user wanted to send a message to a MySpace - they be able to.
Create or Join a Group - I'm anxious ot hear your thoughts on hwo to aggregate or somehow create Groups which woudl shadow each other on different systems. So if I created a group on DiSO called 'Reggae' it would be able to 'bond' with a Reggae group on facebook or MySpace. Uploads, messages, posts, streams, or social graphs could then be synchronzied and updated between systems - and kept in sync. I call these 'meta-groups'.
Synchronize accounts - I haven't seen this note anywhere - so I'll throw it out, as a concept that all would support, and implement in their own way. But clearly keeping disparate accounts in sync is a lo-level verb that almopst all systems will provide. So we shoudl think about how to abstract that to teh pint where at least one synchronizer woudl call a data source and say "last update xx/yy/zzz - any changes?" Are there anys tandards for taht kind of stuff - yet?
Auto-invite = is a verb which we're gonna be using allot. User goes to their social graph (which may be internal or come from a number of different sources) and decides to send out an invite to any/or/all of them. They select the invite list and bam - auto-invite the list.
Add a Friend, establish a relationship - any thought gone into friending between systems? If we believe that people will maintain memberships on mor ethan one system (as I do) then it bears the reason that one might wants to establish frienships across systems.
Comment on something, Rate something - these are actions which one might want to aggregate and keep track of ALL my comments or ratings I've done, across a wide range fo systems. So the action of commenting or rating (or reviewing for that matter or creating events) must be a verb which can then be aggregated. Event created and Review created verbs are a natural.
I'm also a strong believer in supporting the meta-weblog API or nowadays Atom and enabling users to be able to post something externally into a system. So Route a post becomes a key verb.