Service for selectively and proactively notifying users of changes in states of items in an electronic catalog

An electronic catalog system includes automated processes for detecting and handling specific types of browsing events, such as non-conversion events in which users browse but fail to purchase specific items. In one embodiment, when a user engages in a threshold level of browsing activity with respect to an item without making a purchase of that item or a substitute item, and a favorable change in the item's state thereafter occurs (e.g., the price is reduced or the item becomes available), the user is automatically notified of the state change. In another embodiment, when a user transitions away from an item or item category after engaging in a threshold level of browsing activity, a determination is made whether to present to the user a time-limited purchase incentive that is tied to that item or item category.