In the IT world, this happens often. At first it kinda bothered me, but now I've just gotten use to it. Sometimes, these recruiters actually have good positions worth considering (if you're looking). Their game is to call around hoping to run into someone with a potential background match who would consider a new job.
These folks get their names from many sources like jigsaw, linkedin, or any other contact database. If you sign up for professional newsletters, organizations, conferences, events, ect. that's how these folks get those names.