in the US it seems rather easy to sign anyone up for anything provided you dont mind putting down, say, your own home address for some friend or relative you know in the FF sign up pages. Hey, for all the airline cares, you and them all own and operate a multi-family boarding house! This has also worked for me and friends who wanted to combine family account information with BA.

All and all, I have even used the same email address for at least 10 -15 people. It's all done with computers these days... so it can legitimately work, as long as you satisfy the requirements of the sign up process.

MM