Another thing that a reverse cell phone directory is not is an expensive and questionably-reliable private detective you must put your trust in to find all the reverse cell phone number information you seek for you. No, a reverse cell phone directory service puts you in the driver's seat, giving you full control of all your searches.
In the past, a private investigator was the only person accessible to the general public (barring the rare instance of having a friend or relative working for the phone company or the government) who had access to all this information. But now, many legitimate and reputable companies have worked long and hard to gather all the cell phone data you might need, compile it in an easily searchable fashion, and make it available to average folks like us.