[Lonesome in Massachussets]

You make sense, I’ll reserve judgment. When you are a PI, other than being paid to be a PI, what actions do you take that any other citizen could not? As far as I know, PIs have no special police power, no access to records not accessible to the general public, etc. Other than being paid to investigate, what distinguishes a PI from any other citizen?

[Joe 6-pack]

The differences and restrictions vary from state to state. In most states, the primary difference between a licensed PI and a lay person is, believe it or not, being able to charge fees for performing investigative services. Additionally, licensed PIs may be entitled to access certain databases under the DPPA (Driver's Privacy Protection Act), and similar state privacy laws. Also, most states that have stalking laws have exceptions for private investigators performing legitimate investigations. California is a good example as their "paparazzi act" actually restricts some public photography for the lay person, but which exempts PIs conducting surveillance based on articulable suspicion.

You are right; however, for the most part another person can do what most PI's do, they just can't charge for it. A lot of states treat their licensing like any other profession, so it's more for the protection of the consumer who may engage a PI service, so that consumer knows that the licensee has met a minimum of qualifications regulated by the state.