While the concepts underlying user clustering can lead to innovative, highly engaging products, developers should not tread this path lightly. As described in the preceding section, privacy and security should be paramount in any clustering system. If you have to sacrifice features to protect your users, then so be it. Within any social service, the trust relationship between the service and the users determines the product’s success. If implementers of these services don’t care about their users’ privacy and security, they should at least understand that their indifference has a cost. If a user doesn’t trust you, his interaction with your service—which might come in the form of additional profile information or social data that could be monetized through ad targeting or other sales mechanisms—will diminish or disappear completely.