I used to be an executive recruiter and I can tell you recruiting firms usually promise clients they will go out and find top-notch candidates who are already employed and not looking for work (that's what makes them "recruiters" -- they recruit people). But I can also tell you most clients don't pay that much attention to what the recruiting company tells them, they just want to fill the position. So I'd have to say recruiters are probably the ones pushing the "no unemployed" language, because they promised the clients.

But I'm a little surprised if staffing companies are doing the same thing, because staffing tends to be entry or mid-level jobs, not executive or professional career-track positions, and those clients are a lot more concerned with filling the position quickly, with competency and reliability the main criteria.

If you want a job and think you're qualified, ignore the ad and apply anyway:

A recent report by the National Employment Law Project, a worker advocacy group, called out 73 businesses for asking in job postings that applicants be currently employed. "This perverse catch-22 is deepening our unemployment crisis by arbitrarily foreclosing job opportunities to many who are otherwise qualified for them," NELP said in the report.

The Huffington Post reached out to half the organizations cited in the report, and 19 responded. While several staffing firms defended the ads, employers disavowed them, saying they'd been written by a person outside the company and that they were completely unaware of the language used.

For instance, a spokesperson for AIELLO Home Services, an HVAC company based in central Connecticut, said his company would never run a job ad that specified applicants should already have jobs.

"If you like to make money and have a flexible schedule, then a challenging and exciting opportunity awaits you," an online job ad for the company said. "And if you are currently employed, believe enough in yourself and your abilities to make a positive career move...you and your family will be glad you did." (The ad also specified: "NO prior industry experience required!")

After HuffPost forwarded the ad to the spokesperson, marketing manager Phil Clement, he looked into it and then said it was a mistake. "The ad is a pick-up from some consultant who has helped us in the past find sales people," said Clement. "The ad is even copyrighted by him. We've just put our address at the bottom and hoped to uncover one or two experienced sales people along the way."

Clement said his company has no policy against hiring the unemployed. "AIELLO simply wants to hire good people. There is absolutely no policy written or 'understood' that we will only recruit from the employed," Clement said, adding that he himself had been out of work for two months when the company hired him this year.

"As my own hiring should testify," Clement said, "AIELLO definitely hires the unemployed."