Google Search Appliance

The Google Search Appliance ISN'T about Google selling hardware: it's about Google making some money on the side out of a) it's searching and indexing software technology, and b) it's massive brand name.

If they thought it feasible they'd probably sell it just as a shrinkwrap application to go onto other peoples' boxes, but they probably prefer the mystery 'magic box' approach of supplying a turn-key solution.