For a messaging medium that is reportedly dead, there sure is a lot of interest in e-mail these days.
Why? E-mail is the stickiest of applications. For Web sites like AOL and Yahoo, e-mail alone can keep users in the fold. Simply put, you can't have a massive scalable top 5 Web property without e-mail. Sure, some folks will say e-mail is dead--to be replaced with Tweets, life streams and other more current messaging systems--but the reality is most of use e-mail daily and will keep on using it.
Read more of "E-mail mania: Why does everyone want to be your inbox?" at ZDNet.