Its not actually illegal, only according to blizzard. Tomshardware wouldnt be at risk of anything as only the seller of the account would get in trouble and even then it would only be with blizzard not the law...
9.2 Account. NOTWITHSTANDING ANYTHING TO THE CONTRARY HEREIN, YOU ACKNOWLEDGE AND AGREE THAT YOU SHALL HAVE NO OWNERSHIP OR OTHER PROPERTY INTEREST IN THE ACCOUNT, AND YOU FURTHER ACKNOWLEDGE AND AGREE THAT ALL RIGHTS IN AND TO THE ACCOUNT ARE AND SHALL FOREVER BE OWNED BY AND INURE TO THE BENEFIT OF BLIZZARD. Blizzard does not recognize the transfer of Accounts. You may not purchase, sell, gift or trade any Account, or offer to purchase, sell, gift, or trade any Account, and any such attempt shall be null and void.
I highly doubt they're going to take you to court, I've been selling/trading accounts for over 4 years and have been caught plenty, nothings happened to me. They just email you asking for verification that you're the owner and if you don't reply they'll simply suspend your account until you can provide them with the information they need.