- Don't drink if you are not of age;
- Don't drink and drive; and
- Don't drink so much you feel like crap in the morning.
Those first two are laws that exist for our protection, and shouldn't be broken. The third, however, is open to interpretation. I've always found that waking up even a little hungover has detrimental effects on my training for that day. As someone who wants to be the best runner I can be, doing something that negatively impacts my career is, to me, not responsible.
I think the most important thing is that each person finds a balance that works best for them. Beer has decent nutritional value, tastes good, and can be a well-deserved treat after a hard run. However, it isn't a meal replacement, tastes terrible on the way back up, and can add a lot of unwanted pounds if you haven't earned it.