Emily Rockwood (J.D. 2007, George Washington) has published a student note, Privatizing Tax Collection: A Case Study in the Outsourcing Debate, 36 Pub. Cont. L.J. 423 (2007).  Here is part of the Introduction:

This note will address both the philosophical and practical problems involved in outsourcing collection of federal tax debt. It will provide additional background information about the history of private tax collection in Part II and about the American Jobs Creation Act in Part III. Part IV will discuss the problems with privatizing tax collection and Part V will suggest possible alternative ways to increase tax revenue without privatization, particularly by providing the IRS with consistent funding to allow IRS agents to perform their collection duties more effectively.