> but 2FA was both possible and a consideration 18 years ago

You could setup your own dns servers obviously 18 years ago and in fact when starting out in the mid 90's that is exactly what we and many others did. (Criket Liu nutshell books from O'Reilly)

http://shop.oreilly.com/product/9781565920101.do

http://www.oreilly.com/pub/au/284

"I'm wondering how Dyn is taking this. "

I use dyn as well as run several dns servers in different places [1]

My reason for not using this is that it's being offered by google and the obvious fear that they will decide one day to stop offering this, supporting it, or improving it. As I am experiencing now with google voice for example,

[1] Since the mid 90's actually learning from this book:

http://shop.oreilly.com/product/9781565920101.do

DNS and Bind (now in its 3rd edition) by Liu, Albitz, and Loukides. It's an O'Reilly book.

http://www.amazon.com/DNS-BIND-Cricket-Liu/dp/1565925122

I'm not sure which book you are talking about but my guess would be "DNS and Bind". http://oreilly.com/catalog/9780596100575/

Cricket Liu is the co-author of the Oreilly DNS & Bind (Cricket & Grass hopper cover) ~ http://oreilly.com/catalog/9780596100575/ a handy reference for setting up Bind.