Earlier quoted context omitted.
This will enable you to get the private e-mail of the google account that owns the channel, which is not necessarily the same one a channel may give away publicly. So for some channels that provided no contact information, you now can acquire an email address, and for everyone else you may now get an additional one. It also enables you to link multiple channels back to the same person. Every bit of information you ca…
I think we can imagine reasons why this would be valuable. It's a vuln. That's worth know about and fixing. I'm not sure that there are terribly many black market opportunities for "every bit of information" such that this should be a six figure payout or whatever.
- Regime critics with a channel on YT.
- Vulnerable individuals and others trying to keep their identity a secret. Putting yourself on YT means putting yourself in front of every deranged individual out there.
- Trump quite famously runs some of his own social media accounts personally, for better or for worse. And even where he doesn't, he probably retains ultimate control - in the case of YT it might be his personal google account that created the channel. He's probably not the only high value target to do so.
Also if you happen to be in any date leak, being able to figure out your private e-mail address gives attackers another place to check whether you re-used a password.