I'm for closing this as "WONTFIX" also, like it was on trac. I really don't like OpenID idea, for exactly the reasons Kuno (warp) mentioned.
After catching up a bit on OpenID, I don't really see the huge security issues hinted at - if you know what you're doing.
However, one use case for this is to provide MB.o authentication for other places - e.g. https://acoustid.org/. For this to work, MB doesn't have to accept OpenID logins, as long as it acts as a provider.