I am constantly amazed at how people assume an ac compressor is an easy fix. Take a look at the pictures.

This is from a 96-00 Honda Civic AC Compressor This is a scroll design ac compressor. All a/c compressors do the same thing, but many use different designs. You can see the scroll design in the second picture. The 2 scrolls roll around each other at high speeds to heat the refrigerant.

The side of the compressor on this one was actually blown out. The relief valve looked clogged. My best guess at failure is that too much pressure in the air conditioining system built up and the pressure backed up at the compressor. The system was probably blocked at the ac condenser and the pressure never made it to the expansion valve. The relief valve gets clogged and there is no where for the pressure to go. At 300+ pounds of pressure, you can blow out a side wall.

Moral of the story is to do the job properly and make sure the system is clean before starting.