Every Buffalo wild wings that I have been to serves partially filled draft beers. They have an eloborate full page explanation in their drink menu as to why they serve their beers with so much head and they even have a picture of the perfectly poured beer.
The picture shows about a finger or two of head and about the same amount of crown (the portion above the rim of the glass). However, when they pour the beer they serve it without the crown. When the head settles in the tall pilsner glasses that are wide at the top and narrow at the bottom, your beer just went from 22 oz to approximately 18 oz.
They consistently do this on every beer they pour. What a scam!