The ACLU recently released a report on the criminalization of private debt:
An estimated 77 million Americans—one in three adults—have a debt that has been turned over to a private collection agency. Thousands of these debtors are arrested and jailed each year because they owe money. Millions more are threatened with jail. The debts owed can be as small as a few dollars and can involve every kind of consumer debt, from car payments to utility bills to student loans to medical fees.
The criminalization of private debt happens when judges, at the request of collection agencies, issue arrest warrants for people who failed to appear in court to deal with unpaid civil debt judgments. In many cases, the debtors were unaware they were sued or had not received notice to show up in court.
There are tens of thousands of these warrants issued annually, but the total number is unknown because states and local courts do not typically track these orders as a category of arrest warrants. In a review of court records, the ACLU examined more than 1,000 cases in which civil court judges issued arrest warrants for debtors, sometimes to collect amounts as small as $28. These cases took place in 26 states.
The report is available here.