First it was Craigslist asking for your phone number to verify your account. Today while trying to set up a Flickr account using a new Yahoo email address, they wanted my cell phone number to authenticate my account. I would have no problem giving them my business phone number, but I don't care to give Yahoo my cell phone number to verify my email account. I had already given them my recovery email address. So now, I will need to find a work-around possibly purchasing a disposable phone just so I can verify a new Yahoo email address for business use.
So this begs the question...why does Yahoo only want a mobile number vs. any other number?
See Craigslist Phone Verification for conversation regarding CL's requiring a phone number for verification