I think you are right, though the key differentiator is not chatty vs. discrete messages. Chat done right can solve a number of problems that email has:
- Email sucks as an archive. It's fine to store personal emails just for yourself, but when you dig deep and assess how much critical corporate knowledge is locked away in this multitude of personal archives of all employees, you'll be in for a shock. A Twitter-like chat system for corporations (like Yammer) will retain that knowledge for the right group, including its future members. I find that only a small part of my conversation is actually really private between me and someone else. Most of it will be relevant for my team, for another team, for a special interest group within the company, or for the company as a whole. In a corporate Twitter, asking for knowledge is automatically the same as sharing it, as soon as an answer is given. In email, any answer is lost for everyone but yourself.
- Email is fine for communicating 1 to 1 or 1 to many, but it is a poor vehicle for many-to-many conversations. Chat systems (again citing Yammer as an example... by the way I have nothing to do with Yammer except that my current client uses it) can solve this by having private, ad-hoc chat groups in which participants can be invited or drop out as needed. New joiners will see a clear, linear history of what has already been discussed, instead of a steaming pile of replies-to-replies-to-replies in multiple sub-threads, all intertwined in a single email exchange.
In our team, we've tried sticking to the rule that forbids the use of email for anything that will still be relevant one week from the day of sending. The idea is that any such messages belong to the corporate memory, which means email is out as a vehicle for storing it. Instead, people use Yammer or email links to documents stored in a central repository. It worked out quite well, both improving recall from our corporate memory, keeping everyone on the same page and aware of each others' work, and improving the quality of discussions by electronic means.
But we too found that it is extremely hard to break the email habit. One thing that email still has going for it in the corporation is that everyone has it, and everyone is expected to read it several times a day. You might get told of for missing an important email, but being told off for missing an important discussion on some social media thingy? We're not quite there yet.