BungeeBones Members can use their earned advertising credits immediately to purchase their own advertising or they can redeem their earned advertising credits for Bitcoin at a one-for-one exchange rate or they can sell their earned advertising credits to other members (using an online "smart contract") for cash or alt coins.
This system is not designed to be a full fledged exchange (i.e. another "Mt. Gox" or "BitStamp") but rather just a way to make it easier for those that want to advertise and those that have earned AdCoin/Advertising credits (they're all synonymous and/or of equal value) to be able to conduct their own transactions between themselves. Sellers (for the most part) are not depositing Bitcoin to trade but are liquidating their own earnings and buyers aren't buying to acquire Bitcoin but rather to acquire advertising credits that are backed by Bitcoin.