The Chemical & Engineering News blog has a nifty little piece about how to get the perfect amount of foam on your beer. Among the tips was this gem, which obviously made my heart sing:
Wash your beer glasses by hand; dishwashers leave detergent residues that interfere with bubble formation. The lacing of foam on the sides of a glass is actually an indication of cleanliness. Scratches at the bottom of a drinking glass can serve as nucleation sites for bubbles, so don’t sweat the imperfections in your barware.
Cleanliness is next to Godliness but over on its other side it's also next to Drunkeness.