Here is a link to our service page with many answers on it
EGS Middleman Service - eGaming Supply
But basically, a transaction would go like this:
1) You pay through Plimus and post a thread with the sale details and Plimus number, linking it to your original thread
2) A MM will verify the Plimus, then ask the seller to send the the account info
3) The MM will then take over the account (i.e, change all the info and passwords) and verify that it matches what was agreed upon by the buyer and seller
4) Once the MM is satisfied the account is as was described, he instructs the buyer to send the payment
5) When the seller acknowledges receipt of payment, the MM will release the account information to the buyer.
The transaction is then completed.
If the buyer is sending the original CD keys with the account, it is extra protection. Anybody who has the original name and SQ/SA of the account is considered to be the owner by Blizzard. In the event two people have said information, ownership of the CD keys will be the deciding factor.
From my experience, IP tracking only occurs in obvious and extreme circumstances. I have yet to experience such an event with a trade that I have mediated here.
That being said, if you live in Germany and buy an account from China and the MM is located in Argentina, the gaming company might be tipped off as to something supsicious.