Apparently when bars and taverns try to save a dollar or two. From the Wall Street Journal:

Beer prices at bars and restaurants have risen over the past few months, as prices of hops and barley have skyrocketed and retail business has slowed alongside the economy.

Some restaurants have replaced 16-ounce pint glasses with 14 ouncers -- a type of glassware one bartender called a "falsie."

And customers are complaining that bartenders are increasingly putting less than 16 ounces of beer in a pint glass, filling up the extra space with foam.

I'm of the mind that a bar can serve whatever sizes they wish, but if they serve it under the nomenclature of "pint", then I better be getting sixteen ounces of beer. For you beer fans out there, don't stand for this. Either hold them to the pint standard, or find a different place to drink.

(via Law for Food)