How many glasses of beer is moderate?

Are we talking personal consumption? Assuming that a "glass" is a pint, or thereabouts, and a person is a regular drinker, and it is spread over an evening, 2-2 1/2 glasses is probably moderate. If a person is a light drinker, or it's not a whole evening, then less. 2-2 1/2 represents 4-5 units of alcohol - the health recommendation is that people shouldn't drink more than 3-4 on a regular basis.