THIS WAS ONLY SPORADIC A YEAR AGO

To judge by help wanted ads a year ago, only a few of them explicitly ruled out those who were currently unemployed.  Now, it seems widespread:

Job listings say the unemployed need not apply
By Liz Goodwin
National Affairs Reporter
THE LOOKOUT - YAHOO NEWS

Hundreds of job opening listings posted on Monster.com and other jobs sites explicitly state that people who are unemployed would be less attractive applicants, with some telling the long-term unemployed to not even bother with applying.

The New York Times' Catherine Rampell said she found preferences for the already employed or only recently laid off in listings for "hotel concierges, restaurant managers, teachers, I.T. specialists, business analysts, sales directors, account executives, orthopedics device salesmen, auditors and air-conditioning technicians."

Even the massive University of Phoenix stated that preference, but removed the listings when the Times started asking questions.