We accept signed messages as proof of share ownership exclusively.
You're free to use any email address of your choosing, as long as it's linked to a Google account (currently the only OpenID provider icedrill.io supports). It does not need to be a gmail email address, or even the one you used @ bitfunder.
All other securities moving to direct shares accept a signed address as proof of ownership.
No other security moving to direct shares requires adhesion to Google's (illegal) ToS.
If a shareholder neglected to change their Bitfunder address in the 30+ days they had to do so that's their problem, NOT YOURS OR MINE.
It's not your place to force unwilling shareholders to jump through asinine hoops like MANDATORY GOOGLE.
A MANDATORY GOOGLE provision was never in the IceDrill contract and you have no right to suddenly require it.
Forcing people to do something they never agreed to, on pain of losing the money the trusted you with, is called EXTORTION.
All of the overblown talk about 'black holes' and 'reinventing the security wheel' is a sorry excuse to avoid using 2FA instead of OpenID.