Inbox vs. Stream interaction pattern

A recent Tweet exchange with Alan got me thinking on (inter)action pattern in the collaborative software we use. On one hand we have the incumbent eMail: time tested, loved, loathed and under (so the hype) thread from the new kid on the block: activity streams (a.k.a. river of news), in various technological implementations (from propriety, RSS, ATOM, JSON to activitystrea.ms). I'll compare the two from the perspective of work, where you need to get things done ( pun intended). I will use email actions from Lotus Notes as example, available actions in your eMail software might vary. Similar I use IBM Connections 4 as stream example. Here you go:

Purpose	eMail	Social stream
What's new?	Scan inbox, look for unread marks, switch to "unready only" mode	Scan stream, memorise where you left off
Read details	Click on item (with preview pane) or open it	Click on item, then click "show all", "show more", click on right arrow (in Connections 4)
See conversation	Click on triangle to expand or use show menu (when eMail open)	Click on item, then click "show all", "show more", click on right arrow (in Connections 4)
Reply	Click reply (with too many options )	Click comment
Tag a reply	Send & File, Categorize	Use # in the reply
Indicate that you concur/endorse an item	Send a reply	Click the like button
Mark as read	Automatic when previewing or reading	n/a
Associate with something	File in folder(s), categorize (yep, that's like tagging, but not shared with others and in Notes since 1.0)	Tag
Information not relevant	Delete or remove from inbox (my favourite for "might be relevant some other time" since it still shows up in all documents and search)	n/a (in Activities there is tune out, or remove watching a specific tag)
Read later	Keep unread, file in folder(s)	n/a
Associate with a project or a customer	File in subfolder(s) of project/customer folder, use custom plug-in for meta data	tagging is flat only, harder to find later
Followup action needed	Flag for followup, copy into task	n/a (the sharebox might remedy that in future)
Add to personal/team knowledge collection	Copy into journal or discussion db (there's a plug-in for that)	n/a, but you can use the Evernote browser plug-in
Scheduled action needed	Copy into new calendar entry	n/a
Let other people know	Forward	Reshare with @Name in the message
Look at specific information like a project, product, customer	Open that folder, look at the categorized view, fulltext search	Browse for the tag, fulltext search
Suggest filing/tagging destination	Use the SwiftFile plug-in	Look at other people's tags for the item
Suggest what else is interesting	n/a	Social analytics

It seems the interaction patterns for actions in the social space need to mature a bit. Interestingly e.g. Google reader has sorted the problem of read/unread for a stream of news (your RSS feeds) by tracking what entry you focus. Might that make sense for an activity stream (show unread only)?