Data Mining: Text Mining, Visualization and Social Media: Two Minute Rule: Intelligent Email Clients Needed.
In addition, I think that one of the big problems with email is there is no direct relationship between the time stamp on an email and when the sender expects or requires a reply. This can be inferred in part by various priority settings, but these are easy to ignore and often mean different things to different people (an ontological commitment problem if ever there was one!). Perhaps analysis of the content as well as past interactions with the sender could be used to provide a better sorting function...
I'm a synchronous communications type of guy. If it's got to be asynchronous then say it on my blog or even on yours, but don't e-mail it (unless you have to).