I was hearing noise before discovering the crack, then the pinging stopped. A short while later is when I found the crack.
There isn't any more noise coming from the bike anymore. This is why I suspect that the crack won't cause the frame to fail. This may be wishful thinking, but even after the crack I continued and will continue to ride it out.
I'm also curious as to how long I can keep this bike on the road. It may tear, as cyccommute has described. I have to take this risk. I'm not in position right now to do anything about it and I need this bike to get around.
Only time will tell what my or my not occur. In the meantime I'll have to look for a new frame.