Then you might say, "But there is also a public feed of all the tweets" to which I would reply, "There are plenty of public interfaces to mailing lists". Gmane is essentially twitter if everyone used tags and tweets were actually given context in the larger conversations they create. And there was a lot less worthless noise.

There is nothing new here. Basically, Twitter just took away the ability to specify a group of recipients when sending an email, limited the character count, removed file attachments, etc.; Yammer put those features back. I hope Yammer becomes super popular because eventually someone else will then notice, hey, we're essentially using email again!

Yes, I'd agree that it matches features with a mailing list but the types of messages that are posted on Yammer would be unacceptable to send as a company-wide email. People mostly post updates about where they are, conferences they are attending, and if they're working from home or remotely. Marketing-types tend to post links to the latest techcrunch or gigaom article. Designers tend to post the latest links off of delicious/popular. As far as the character limit, its treated just as twitter and no one posts anything too large.

With a corporate-wide mailing list, everyone would have to read every single message. People tend to correlate the number of recipients with its importance. Yammer messages can be easily ignored and read at leisure. As a poster, this naturally diminishes any inhibition when firing off a message. Perhaps it's just the obvious outcome of a messaging infrastructure wholly separate from our corporate email, which has expectations and political baggage. Maybe this says something about the state of email tools...

Having said that, my first instinct upon reading this feature list is to suspect that you're right. Yammer has too many of email's features. They need to leave more things out. Otherwise the pathological behaviors that characterize corporate email (poor composition, unclear expectations, inbox overload, endless chains of quotations, complex workflows, reliance on cut-and-paste versus publish-and-link, the use of Microsoft Office attachments) will just port right over, and nothing will change.

I'm guessing that removing the character limit will prove to be an especially foolish design decision: Who wants to read five-paragraph Tweets? And file attachments are probably even worse. One of the charms of Twitter is that it refuses to allow such dinosaurs. Instead it forces you to adopt an amazing modern technology -- the hyperlink -- to point people at your blog, or your Flickr set, or your Slideshare page, or your Scribd page, or your github account.

As twitter has shown, there's value in the posting of notes about what you're observing, reading, thinking. I like to think of it as messaging without guilt. Email, IM have a certain social expectation, microblogging doesn't. I like the way Alan Lepofsky put it: "Email is 'reply hoped for'. Instant messaging is 'reply expected'. Social messaging/microblogging is 'reply optional' (http://bit.ly/dm03).

The principle here is that people are so much more than the jokes they email, and the requests they send to one another. There's a whole lot of smarts people have that do not have a channel. And organizations are the poorer for not providing a way for employees to contribute these things they know and dream up.

Once this notion of commenting without guilt takes hold, a lot of what employees express becomes conversational material. And where will that happen? Likely within the microblogging app, not email.

I used Twitter for about 8 months and during that time I don't think I read a single valuable tweet that didn't contain information that I shortly found through some other channel. Most tweets were pure noise. What was worse is that I joined in with the noise and I am not the sort of person to broadcast what I know to be irrelevant information. Suddenly because everyone was wasting my time, it was okay for me to waste theirs.

Yes, microblogging may be increasing commenting, but those comments are largely noise; most people can only cite specific instances, usually revolving around real-time events, where Twitter was of any real use to anybody. There is a cognitive cost to reading all those tweets, not to mention a time cost, and I found that those costs far outweighed any perceived benefit in almost all cases. With a mere 140 characters to convey information, it seems like this would be the case of the majority of the time.

Microblogging takes the friction and guilt out of speaking (essentially), which I think is bad. You should think before you write or speak. You should ask yourself, "Is this information of significant use to a majority of those who will be subjected to it?"

    Unlimited character length: Email started this fad!

Not sure where you've worked, but corporate email is horribly broken. Those crusty old decision makers are getting hundreds and hundreds of emails a day and would like a reprieve.

The only barrier is user infamiliarity with newsreaders. But newsgroups are close enough to e-mail that there should be plenty of carryover.

It raises the question. Begging the question means something else. Look it up.