I just finished the silver challenge mode so I could get the yeti mount. What I noticed is that the mount is account wide, but the title is not. When I completed the last cm, all characters online on that bnet received the mount in the mail. I learned the mount on one account and put the others in the bank.

As I 10 box and have 2 bnets, I then xfered a toon with the yeti in the bank to my second bnet and learned the mount on that account. It worked perfectly and now I can run around on 10 yetis.

I think this would work with almost any mount or item that is mailed to you as long as it doesn't require any kind of requirement to use or learn. An example would be the the core hound mount. It was also sent in the mail as I'm sure many of you guys know. I stuck the extras in the bank so that so that I cound possibly learn it if I ever have another bnet in the future.