Serious work drinking? No. My nature of work is one where it wouldn't be physically dangerous (i.e. working with machinery or heavy equipment), but everybody has far too much to do, not to mention the potential for embarrassment should it impact work quality.

But every company I've worked for has observed weekly Beer Fridays, where beer magically shows up in the fridge and most people will crack one open around 3-4 pm. On certain Fridays, special circumstances (i.e. celebrating completion of a large project, wishing a departing employee well, etc.) dictate that the beer is replaced with fine Scotch, always in the same timeframe and level of moderation.

We've never had any issues with it. Everybody knows taking it to excess would mean the end of it. My employers have all been the variety that don't confuse activity with results... they recognize the contributions (and often, long, hard hours) that employees have put in all week. So when Friday afternoon rolls around, they allow them to be human and socialize/unwind a little bit before heading home for the weekend. It fits in perfectly well with a high performance culture.