Rim cracks on spoke adjustment holes, how much should I panic?
To me, it looks like whoever (or whatever, as it was likely machine built) used the wrong size tooling to hold and screw the spoke nipples as the wheel was built. Not a rim manufacturing defect but a wheel building defect. 

If it's still under warranty, I'd get the wheel replaced. Any cracks are bad cracks and could propagate. If it's not under warranty, I would keep an eye on it especially if you put aggressive loads on your wheels (mtb, touring, etc).