On their official page
for Star Wars: The Old Republic, BioWare has issued a statement for gamers to be weary of fake offers to join the game's beta-testing.
Furthermore, the sale of accounts with access to the Game Testing Program is strictly prohibited by the Game Testing Agreement. We closely monitor the activities of all accounts involved in the Game Testing Program, and are quick to notice accounts that change hands. In the event that an account in the Game Testing Program does change ownership, we immediately take action to the fullest extent possible, including permanently banning the account from the Service.
They also run users through their official process for beta-testing, and what to look out for in the event of being invited to participate, so make sure you check it out and arm yourself with knowledge, oh Padawan.