B2B companies that implement SSO will therefore rely on the work address of their users, but some communities can be valuable after a member is no longer a customer. Think of InSpired: Today I am at Smartly.io and my account on InSpired is tied to that email address. But if I leave and become a community manager elsewhere, or introduce InSided to a my new company, wouldn’t it be nice for me to retain my status and network of 1-1 communications within InSpired?

While switching email address could be a problem how about a recovery email address? 

I’ve actually spent quite a bit of time implementing this via the InSided API using a custom field which seems to work well. However this is very custom and I’d much rather it was supported out of the box! Happy to share more if there is interest of course.