Speaking from personal experience:
is used as a blood thinner. Alcohol will do this as well.
Because of this, you are heightening your risk of uncontrollable bleeding should you cut yourself. You are also at risk of bleeding internally.
Although I have never experienced any uncontrollable bleeding from open wounds as a result of drinking alcohol while on warfarin, I have noticed that I get big red marks under my skin, specifically around the ankles, as a result of this practice.
The bottom line is that you should consider limiting your alcohol intake while on warfarin.
Please refer to the following page for medical advice:
FDA GUIDE FOR COUMADIN/WARFARIN