We're going to start to do small (like a dozen people) invitation-only tastings (well, drinkings...tastings are for trying to sell wine--this is just for wine geeks to drink some high quality juice) for some of our special customers.  I was considering estimating about 1/3 bottle per person.  Too much?  Not enough?  Thoughts?

Depends on the # of wines and how much people want to drink. For comparison reasons we use a 2 oz cup to pour at a poker group whenever we have 10-12 people in attendance and we usually have 6-8 wines to try. At 8 wines and 2 oz's per, that works out to 2/3's of a bottle per person... but then again we're pretty big drinkers ;)

I think a 2 oz pour (59ml) per bottle for 12 people is fine.

Depends on how many bottles you're letting them taste. I wouldn't pour more than 2/3 of a bottle, total, for a customer if it was at your store. I'd let the # of bottles dictate your pour, vs. a set size. Realistically, if it's a special group of people, you'll pour more for some and less for other based on what they can handle, cosidering a drive home from a retail location.

In terms of BAC, you want to keep it below 1/2 bottle per person. Also, the time involved is important. Remember, your store will have liability for those drinking there in case something goes wrong.

Indeed. Disclaimer planned at the start of the evening. BTW, tonight's lineup:

2002 Flora Springs Out-of-Sight Vineyard Cab
2002 Flora Springs Wild Boar Vineyard Cab
2002 Flora Springs Holy Smoke Vineyard Cab
2005 Numanthia Numanthia