Yes. When you sign up for an account you can use it for both the selling and buying ads. All earnings (or account loads) are placed into your account balance for spending or withdrawal.
*In the case of a refund, account loads must be refunded back to the original source. (i.e. PayPal loads can only be refunded to the original PayPal account, Paxum loads back to the original Paxum account, etc.)