Why would someone want the serial number of my cell phone?

I’m selling a new and never used BlackBerry cell phone on ebay and a buyer wants me to give him/her the serial number before placing a bid. I asked the individual why and got the following response:

“Because Verizon told me to get this number before buying a phone off e-bay so that I can check the number against the Verizon lost/stolen list because if it is on that list, they have to keep the phone and then I am out of money and a phone”.

Are there any reasons why I should not give out the cell phone serial number?