Agreed. That was the point I apparently failed to make clearly: tweets are ephemeral. You read them or not, but you never care about them a week later.

That is the critical difference with email (and not the broadcast aspect).

"twitter is like email: the other side is expected to read at her pleasure."

Well no. You can't expect me to read your tweets. If it's not in my inbox, it's not important. It's just "fun to know"…

In what way am I expecting too much?
I didn't understand the point you're making.
Can you clarify?

well then, you are expecting too much from your audience If I'm off twitter for a few hours, I may scroll back a bit, but in most cases I would not bother. since you are broadcasting and not sending to a specific person, don't expect the one you intended to get it to get it, unless you used a direct message (which then shows up in her mailbox anyway)

I had a friend who invited "everyone" on twitter to a pretty important event in his career and was a bit surprised to find out I never heard of it…

Hi,
Thank you! I would now go on this blog every day!
Hobosic

I respectfully disagree.
I believe the distinction between IM and twitter is temporal: immediacy v read-whenever (which is where the blogging analogy comes in).
So in the immediacy aspect, twitter is like email: the other side is expected to read at her pleasure.
The difference with email has more to do with the way people retain stuff.

I think this will become important when the Wave hits us. They are mashing up many forms of communication, and then we will need to better understand our own wishes in terms of immediacy and retention.

I think Email is the wrong comparison, they call it microblogging, first of all, but then some people use it for chatting like IM.

then again, I know some people who always delete their mail after a while, keep no archives or sent messages. all idiots, of course…