With TOFU, "priming" equates to blind trust in practice. This is an important point even when you don't nuke on browser-quit. You can have TOFU (e.g., SSH), WoT (e.g., PGP), or PKI (e.g., TLS)... each with it's pros and cons. I can only hope that someday we have something without the "priming" hole of TOFU, the UX hurdles of WoT, and the fact that HTTPS doesn't really stop people from being phished.

I think opting in to the server side checking (which is a bit like the domain-based blacklists that modern browsers have, I think) is the best thing we've got at the moment, so long as that channel isn't compromised.