P2P systems constitute nowadays an increasingly important part of the online world that needs or will soon need all kinds of e-commerce services and applications that are normally available today on client-server platforms. When designing new e-commerce solutions in P2P particular attention must be paid to masking autonomy of the peers and the lack of any central authorities as two most important problems. In this paper we explore possibilities to bring e-commerce into P2P and propose a double auctioning mechanism that does not rely on the existence of central authorities, auctioneer in particular, and is amenable to implementation in P2P environments. The mechanism has good economic properties such as, for example, fast convergence towards efficient trading through intuitive and simple bidding strategies.