One problem related to front suspension has been reported for the 2008 Audi RS4. The most recently reported issues are listed below.
Audi Rs4 suspension components fail prematurely and can cause handling/control issues. After searching online, it appears to be a well documented problem without an official recall. Audi Rs4 suspension includes a component called drc (dynamic ride control) which has an oil-filled bushing on top of the shock strut. This component fails regularly and leaks oil down the strut (sometimes pooling on the ground as in my case). The failure can affect handling and ride quality of the vehicle.