[danaris]

The problem is, as I noted, spending $100 to post a completely bogus job 100 times is basically nothing to even a medium-sized company.

The asymmetry in power & wealth means that if you want the $1 spent by a job-seeker to even come close to the guarantees you describe, you'll probably need to make the company pay $100 per posting or more. And that would effectively require some pretty widespread and strictly-enforced regulation/legislation.

If you're going to have to get that just for this middleman solution, why not go all the way and have the regulation mandate that any job that a company posts has to be real, with full intent to hire, and every single applicant must get a timely, non-canned response?