The most important part of this: "With that said, I think it’s a bad idea to use a @gmail.com address (or any other domain name you don’t own). If Google – or your email service of choice – does turn evil or shuts down, at best you have to change your email address, and at worst they own a critical part of your online identity."

I understand that some people are too lazy (or whatever) and use Gmail. But do you really assume that you won't switch your mail or chat provider for the rest of your life? That's exactly like the people who used @hotmail.com a decade ago.

Your own domain costs $10-20 per year and it's trivial to setup (either on your own server or with Google Apps). And if you decide at some point that you want to switch to another provider, all you need to do is to point a few records (MX, XMPP, SPF) to your new provider - this only takes a few minutes to do.