Why should the onus be on Ancestry?
Explain to me, and others, exactly why Ancestry should commit the time, money, and resources to implement such a system for those unwilling to open a e-mail account to recieve the invitations?
What e-mail addresses won't accepts an invitation? and why?
Sounds to me like they should be looking for a new e-mail provider rather than expecting a company to cater to them because they don't want to do something.
They have the means to solve the invitation problem- if they choose not to do so then why should Ancestry or anyone else worry about them?
Imho, this is an absurd suggestion on the face of it and I certainly hope Ancestry has better business sense than to even consider the idea.