Various computer-implemented services are disclosed for assisting users in selecting items from an electronic catalog, and for selecting merchants with which to conduct transactions. One such service detects when a first user accesses a web page associated with a particular merchant, and then attempts to identify, from a set of users who are affiliated with the first user, a second user who has engaged in business with this merchant. If such a second user is identified, the service notifies the first user, and provides an option or information for the first user to contact the second user regarding the merchant.