Yahoo has a really crummy recovery system compared to the big 5. If things really go wrong, Google will let you recover your account provided authorized forms of identification -- obviously forgery is an issue and Google is very thorough with regard to this (like checking if the account is still being used by the regular IPs or has gone inactive.)

Yahoo on the other hand basically tells you "go fuck yourself." I literally had a Yahoo agent curse me on the phone after I asked for the supervisor. And then she hung up. I gave up on recovering my parents' yahoo account. Yahoo deserves the demise it suffered. Unlike the big 5, its processes are kludgy, even when it comes to customer service and people stuff. Good riddance.