Did you guys not read about the "News of the World" hacking scandals?? It's not very difficult for somebody with the right technology or the right "connections" at the cellphone company to hack my email inbox. I don't like the idea of giving you my mobile number anyway. I can think of many different ways to make a completely secure log-in. (The so called "secret" questions make the system LESS secure, by the way. The answers might be known to siblings, ex-girlfriends, co-workers, and, in some cases, anyone with access to a facebook timeline. The questions you ask are of such a nature that they are almost public knowledge.)Asking me the name of the street I grew up on is not particularly secure if I grew up in a small town that only HAS a few dozen streets.
The so-called "back door" for forgotten passwords should be even MORE secure than the password itself.