It's been so long since I have written (and mailed) an actual ink-on-paper lick-a-stamp kind of letter, that I almost forgot how to do it. It's been years. I pay all of my bills online (and have, the better part of a decade). Cards etc. are delivered personally. Correspondence is via email or iChatAV or RSS.
I just had to send a letter as part of a travel claim, and it took me a while to remember how to do it. I remember waaay back to my high school days, where they teach you about the format of letters, and how you put salutations etc... I wound up falling back on MS Word's letter wizard. Thanks, clippy (you evil sack of bits!)
If I had to guess, I would say we likely have a whole generation of young'ns who couldn't write and mail a letter to save their lives. Sadly, I think I'm slowly falling into that category ;-)