re: I've heard these warnings before
The CME is travelling at 15% of the speed of light, meaning it'll flash past earth so fast we won't even know the exact time it arrived. Previous geomagnetic storms only caused occasional disturbances in telecommunications, dubiously attributed to solar activity. We do have continous monitoring of the earth's magnetic field however, and if we have that, it must be important for something. Don't ask me what though. Maybe just pure science.