Abstract: Techniques are described facilitating transactions involving items or services or information about the items or services (“ISI”) and users. Sometimes, an automated ISI Transaction System coordinates ISI transactions by matching users with ISI with users demanding that ISI. The types of ISI involved may vary, but may include ISI such as clothing, furniture, electronics, books, tickets, video games, computer software, etc. The operation of the ISI system may be enhanced in various ways, including by selecting appropriate users to receive opportunities to sell or supply ISI available from those users, such as in a manner to balance supply and demand for ISI, and by notifying the selected users of those opportunities. The operation of the ISI system may also be enhanced by selecting appropriate users to receive available opportunities to buy or demand ISI such as in a manner to balance supply and demand for ISI.