I use two-step verification for just about any account that allows you to use it. For me, especially, it is critical to do so.
The most important account to have two-step enabled on is your email account, which in my case, is Gmail. That account is the central hub to everything you do, since all your other passwords can be reset through your primary email.
And since all of the HTG-related accounts use my email account, if somebody was able to hack my email, they could take control of the site.
I really hope that everybody eventually provides this feature.