It has long been the standard practice in medical testing: Give drug treatment to one group while another, the control group, goes without.

Now, New York City is applying the same methodology to assess one of its programs to prevent homelessness. 

...

But some public officials and legal aid groups have denounced the study as unethical and cruel, and have called on the city to stop the study and to grant help to all the test subjects who had been denied assistance.

From the New York Times. 

It always amazes me when people think resources are unlimited. Why is "scarce resource" such a hard concept to understand? I don't mean that merely rhetorically. The point is so obvious to many (eg, folks affiliated with IPA and JPAL), but yet in public dialogue some argue as if there are no tough choices or tradeoffs. Who made them gabazillionaires?? Even Bill Gates and Warren Buffett have tough tradeoffs to make.