  Mechanism design has traditionally assumed that the set of participants are
fixed and known to the mechanism (the market owner) in advance. However, in
practice, the market owner can only directly reach a small number of
participants (her neighbours). Hence the owner often needs costly promotions to
recruit more participants in order to get desirable outcomes such as social
welfare or revenue maximization. In this paper, we propose to incentivize
existing participants to invite their neighbours to attract more participants.
However, they would not invite each other if they are competitors. We discuss
how to utilize the conflict of interest between the participants to incentivize
them to invite each other to form larger markets. We will highlight the early
solutions and open the floor for discussing the fundamental open questions in
the settings of auctions, coalitional games, matching and voting.
