Apple acknowledges some Mac Minis have defective analog VGA out

Troubleshooting: Reduced brightness with some VGA displays and Mac mini

...If you tried all of the steps above and the computer still won't display video as expected, contact Apple technical support (1-800-APL-CARE in the U.S.) or take your computer to your local retail Apple Store or Apple Authorized Service Provider (AASP) for diagnosis.

So they've finally acknowledged this defect. Overall, however, the Mac Minis have an exceptional reputation for reliability.