My guess is that there's no easy way to get bulk telephone data for free. If there was a government service that linked everyone's identity to their telephone number, then it'd be easier to scrape it and publish it online for free. As far as I know there's no easy way to get people's real name from a number besides purchasing a bunch of different marketing/caller lists. This is expensive so you probably can't make a profit just by running ads. Plus I bet Adsense has rules against you running ads on a site that gives away personal info. Just my guess though.