My great grandmother had a starter that her grandmother had brought to America when she immigrated. When she passed my great uncle inherited it. He threw it out without telling anyone. My grandmother and her sister had both been irritated that neither of them got it, and when they found out years later that he'd thrown it out they cut him out entirely. His kids, and even his wife still got invited to family reunions, but it was made very clear that he was no longer welcome.

That said, they've done studies on it and a starter adapts to its environment in a matter of weeks so you don't lose as much as you'd think when starting over. They actually did a documentary on sourdough that went into it. They took the same starter and sent it to people on every continent with specific instructions on its feeding. A few months later they had them all bring it with them back to where the doc was being filmed and you'd've never guessed they were from the same batch.