COFlyBoy
Line Up and Wait
To me, a failed ASI is an emergency situation, because I haven't been trained in no-ASI operations (nor is there any mandate for such training). It's an emergency that requires "immediate action," because there is a need at all times to maintain a safe flying speed, and to avoid situations where circumstances could combine with the ASI failure to create undue hazard to myself or others.
An ASI failure will not render your aircraft unsafe (in VMC). 91.205 makes it clear that an ASI is required for legal flight, but doesn't require you to declare an emergency. There are many other ways for a pilot to ensure that he is maintaining a safe flying speed.
I suggest you get with an instructor and spend an hour finding out how easy it is to fly w/o an ASI. Then you won't have to gum up the works with an emergency, you can simply turn to the nearest airport and execute a beautiful and normal landing.