The Tennessean reports in this article that the difficulty of getting driving documents in Tennessee has spawned a system of bribery tied to the Tennessee Department of Motor Vehicles. This week, six people were charged in a criminal sting operation called "Crooked Highway" that targeted a Franklin County driving school that hawked fake documents to ineligible applicants and bribed DMV employees to issue them licenses. Many of the school's victims were immigrants.
"The investigation, dubbed Operation Crooked Highway, has been under way by federal and state agencies for 18 months, Vines said yesterday."
"Federal officials say two immigrants directed people, many immigrants themselves, to Winchester Driving School in Franklin County and paid for fraudulent third-party certification. In turn, the driving school allegedly paid two Department of Motor Vehicle clerks to provide licenses to those certificate holders."
The Nashville City Paper reported on the operation in this article
This same investigation led to charges against two other people in 2005, as mentioned by the Tennessean here.
update: The Associated Press has also published this article which hints that the requirements for obtaining driving documents are strict but that the requirements are easily bypassed. According to this article in the Chattanoogan, some Tennessee state senators are calling for stricter requirements.