Speaking of block chain bloat:  the existing state of affairs actually incentivizes the practice of "bitcoin change":  If a merchant wants to sell something for 1 Satoshi, he can make a deal with his customer:  the customer sends the merchant 1BTC and the merchant sends the customer back 0.99999999BTC.  This way, no transaction fee is required.  However, it clogs up the block chain more than if the customer simply sent the Satoshi directly.