Underage Drinking

I don't mean going to a bar at fifteen or being a hardcore alcoholic before 21. I mean the smaller stuff; drinking a glass of champagne on New Years, and getting wine at Christmas when you're still technically underage. 
Or parents buying beer for a sweet sixteen or other special occasion.
Is it right? Wrong? Technically illegal, but everyone does it? 
I think it's pretty realistic to say that most people have tasted alcohol before they're 21, despite the law...and I think it's fairly unrealistic to expect that to change, unless you go to draconian measures. And obviously the police aren't actively bursting into houses and busting parents who give their kids a taste of alcohol.
Thoughts? 
1.Is it...OK to let your kids taste alcohol?
I'm of the opinion that tasting alcohol is fine...with the logic that if you deny it to them, they're going to get it elsewhere and probably in larger quantities than a taste.
2. Is it further OK to buy them limited (or not limited, I suppose) quantities for special events?
I don't think alcohol should be bought for minors just because it's a special occasion; while tastes are fine, they aren't adults and probably shouldn't be drinking like one.