This is such a difficult question. If I knew the parents and was sure that they would be there for the whole party, then maybe I would let my DC take lager or cider, but definitely not alcopops, wine or spirits.
As other posters have said, house parties can easily get out of hand nowadays. Many DC invite loads over when the parents are out/away and it seems that many don't have any idea how to treat things. I have heard from DS1, who has a very active social life, of many horrendous house parties that he has been to. Parties where toilets have been broken (as in smashed), carpets wrecked, etc.
When I was 16/18 we often had house parties. All the furniture would be moved out of one room into the garage, any horizontal surface would be covered in plastic. The drinks/food would be in the kitchen and, most importantly, my parents would be upstairs, everyone would know that they would be upstairs and they would come down once or twice, just to check. I have fond memories of those parties. It all seems a bit more hardcore nowadays. It's ironic. People won't let their DC walk to school, stay at home on their own for more than a couple of minutes when they're younger, but don't seem to check on their teenage DC.
Are you sure that your DC even wants to go to this party? Sometimes, they really do want you to say "no", even if they grumble about it to their friends. It's easier for them to say that you won't let them rather than to say that they actually don't want to.
As is the case with so many decisions that we make re our DC, only we know them and we always make the best decision at the time, that we can. I try to be as little judgmental as I can with other parents, as I am not walking in their shoes.
I also agree about making sure that they know that they can ring you at any time if the party seems to be getting out of hand or if any of their friends seem to be in trouble. That's what my parents did and it worked very well. I wouldn't be telling them/their friends off, either. The only time I did was when DS1 (18) told me he was going to take vodka to a party. I told him I thought it was a bad idea and that beer would be better. He still took vodka, drank it very quickly and was brought home by a friend very much the worse for wear. The friend slept in DS's bed and DS spent a very uncomfortable night on the kitchen floor, with me staying up nearly all night beside him as I was so worried. He hasn't done that again.