This may or may not be helpful info for some of you, but I have both a signature and a platinum card. I got the platinum card in August 2007. (So I could have a second companion fare ticket - where I live, it's highly worth it). At any rate, for those of you lamenting the loss of your platinum card, I believe you can just go online and apply for a platinum card. It worked for me.

http://www.bankofamerica.com/alaska_...alaskaair_plat