When service of process was first instituted, it was performed by sheriffs or deputies, and agents of the court. This became a burden on law enforcement, so the legislation was changed. Now, in many states, any US citizen that is not a party to the case, over the age of 18, and residing in the state where the matter is to be tried can serve papers.
Keep in mind that process serving laws differ from state to state and may change. Some states require a that process server be licensed, some require registration with the county and in some states they are required to post a surety bond. Visit the state rules of civil procedure to learn more about service of process in your state. At eServe we believe you will get the best results by using a local, professional process serving company over the sheriff.