How does the unique relationship between human service organizations and the populations they serve impact ethical decisions?
First, I doubt if it is unique at all. Often government agencies form close relations with their customers.
Then to the question. HSO are made up of humans, and when humans see urgent needs, bending rules is sometimes done to help solve the needs. The ethics comes to play when the spirit or the letter of the law is ignored or broken. Some see it as compassionate, others see it as illegal, and immoral.
We see this in Food Stamp eligibility, emergency housing grants, medical care, visitation of the infirm, and so on.
But again, I don't see any of this as unique. The Small Business Administration has a sortid history on who gets SBA loans, and relationships have (gasp) lead the Federal Housing Administration through some dark scandals leading to the very top of the organization.