I had one nebulous recruiter call my company's front desk and try to get me consider taking a position with his talent pool after I ignored his message on LinkedIn.

To my limited understanding, the way the recruiting market works is recruiters build up a bank of talent they can submit for client jobs and they get a % commission of the meat err recruit's base salary as compensation. Ergo, the incentive is to build as big a stable of developers as possible that you can keep submitting for jobs. I personally ignore all the meat market recruiters on LinkedIn, it just gets absurd after a while.