Since the invention of telephones, people have been able to learn anyone's phone number that was not unlisted by searching in a phone directory or by calling directory assistance. In recent years, a new twist has emerged on this called reverse phone lookup. This allows a person to find out who is the owner of a known telephone number. The ability to learn who owns a specific phone number has advantages and disadvantages.

Advantages

Certain people and groups have determined that calling at certain times of the day have a better chance of catching someone at home. These times are usually right at dinner time and at bed time. Telemarketers and bill collectors are the two main groups of people who call at such annoying times. One practice they have adopted is using cell phones to place these call. Many do this because of the ability to purchase free long distance plans rather than pay for business long distance.

It is sometimes difficult to trace the owners of cell phones. Difficult, but not impossible, there is normally a fee associated with using a reverse phone lookup for cell phones. This is because this information is not a matter of public record in the sense that directory information on land based phones is. Learning who owns a particular cell phone provides the means to put a stop to unwanted calls and allows for prosecution if your number is listed on the do not call registry and the telemarketer is trying to circumvent this law by using a cell phone.

Harassing calls are another good reason to use reverse phone lookups. If someone is calling your home or your cell phone with obscenities or making threats, a reverse phone lookup may be the tool needed to help the police make an arrest or the phone company block the calls. Even calls made from a pay phone can be traced using a reverse phone lookup. If a person is calling repeatedly at about the same time each day, the police can arrange to watch that phone and arrest the offender for harassment.

Bill collectors are another source of harassing calls. The law places limits on the number of calls they are allowed to make before they cross the line into harassment. Some collection agencies have attempted to circumvent this law by outsourcing these calls or using cell phones. If a phone number can be traced back to the collection agency and a log of calls created that shows a violation, legal action can be taken against the offending company.
Disadvantages

The single largest drawback to the advent of reverse phone lookup technology is the loss of privacy. Anyone who has your number can run a reverse phone lookup and find out several personal details about you. If you use a cell phone or have an unlisted number, the companies providing the reverse phone lookup must use databases that contain a lot more information than just names and addresses. This information is often made readily available to the person paying for the reverse phone lookup.