We cannot possibly hope to enumerate the set of reasons an agent might have for preferring one set of answers over another, and we should not try to do so. It should be up to the individual buyers to decide what items belong to the same good category, each buyer clustering items in, possibly, different ways. There are two main characteristics that set this economy apart from a traditional economy. There is virtually no cost of reproduction. Once the information is created it can be duplicated virtually for free.
All agents have virtually direct and free access to all other agents.
If these two characteristics are present in an economy, it is useless to talk about supply and demand, since supply is practically infinite for any particular good and available everywhere. The only way agents can survive in such an economy is by providing value-added services that are tailored to meet their customers' needs. Each provider will try to differentiate his goods from everyone else's while each buyer will try to find those suppliers that best meet her value function.