E-Mail Use Falls as Young Chat and Text 

The NYT discovers teens and young adults, who think the relative slowness and formality of e-mail is "so lame," are texting like maniacs. Facebook's new Messages product (which I've tried out—it's pretty good) tries to adapt to the new trend: while users finally have an e-mail address @facebook.com, Facebook e-mail is more like texting or IM, where pressing enter sends the message instead of starting a new paragraph.

And there's another thing:

The company decided to eliminate the subject line on messages after its research showed that it was most commonly left blank or used for an uninformative “hi” or “yo.”

I'm pretty sure I'm guilty of this myself.