How hard do you think that it is to put your own people search engine out there for people to use? It's pretty difficult, isn't it? This isn't plain old HTML. This needs to have a complicated back end that can interface with the various databases and be able to search by specific items like email, social security number, name, and telephone number. I guess that inventing your own is out for most people.
Would you be surprised if I could point you toward one where you can brand your own people search engine and have many different profitable tie ins alongside the actual people search mechanism? There was once an unemployed Washington, D.C. man (he's obviously self employed now) who discovered the popularity of this type of search and decided to fill the niche. It worked so well for him that he became a millionaire with it. Later on he discovered that he could allow people to re brand his search engine and make profits with it, on a smaller scale than him, but still averaging in the hundreds to thousands of dollars monthly. He does this because he earns so much from those tie in sales of products and services that I mentioned, that the companies which provide the commissions give him a smaller commission on YOUR sales, thus increasing his overall profit. Pretty smart guy, huh?
There is also proof of the earning potential which is provided, so that you do not have to simply take all of this on faith alone.