I have one for my 10 boxing and I just removed it. A friend of mine 5 boxing had a problem with his and it stopped working. In order to get his accounts back he had to provide Blizzard all his personal information (no bid deal...) as well as all serial numbers for each of the accounts.... (accounts*3).
If you're like me you'll have trouble finding it, I even did some online upgrading and don't even remember where I put my serials... It took him one week to get it all again running. Since it takes about the same time to get your account back and restored when hacked I removed it from all accounts.

It's just too damn bureaucratic, authenticated personal information should just do the trick... not farming for serials!

I'm not encouraging anyone to do so, just wanted to tell you about this.