Alright, i found out about this on a different site quite a while ago, but haven't seen it on this site yet.
I just read the one where you open the box in store, take a picture, and if you get caught tell them you wre checking to make sure everything was in the box.
I believe mine to be safer, but it does require an initial investment.
What you do is you go to the store and purchase WoW or TBC. DO NOT OPEN IT!
Once you are back at your house, carefully take a razor blade, or X-Acto knife etc and cut along the 'seam' of the box. The 'seam' of the box is where the cardboard is glued together. On the WoW box, open the front 'page' of the box and where the 'page' and the box meet is the seam.
You have to be delicate as you dont want to leave an appearence that it has been tampered with. Patience is always good, take your time. once you have cut the seam open, carefully pull the top and bottom tabs out and you should be able to get the CD's out. Write down the cd-key.
Put the CDs back in the box, glue it back up (I use Super Glue as it dries fast). Of course be smart and try to make it look like it hasnt been opened or anything.
Take it back to the store and tell them a bullsh*t story. "I got this for my birthday from my cousin but he didn't know i already had it, so he gave me the receipt to return it" If they try to tell you that you cant return it, make sure that they know it is 'unopened'. You will get your money back and have a new account.
I have never had any problems with this personally. But I also dont use it too often as I try to keep my accounts unbanned. But I use it to get my friends TBC, or when they need an acct to xfer a char to Etc.
If anything is unclear, post here and I will try to make it more clear.
I don't know what to Tag this as, my apologies before i get the warning.