--It's a terrible idea because we are so excessive by nature. I think that it sets a bad example for our children, for our family, for our friends and for the secular community. It is a stumbling block for many and a weakness for others. Being considerate and conscientious would generally seem to preclude social drinking. Unlike food, alcohol isn't a necessity, and since it's abuse is so common, eliminating it completely is often easier than trying to exercise restraint and drink in moderation.
--I suppose whether it's a sin or not depends on how you define "drunkenness." Is it just a "buzz" or falling down drunk? The elements of not allowing yourself to brought under the influence of a substance, and honoring God's temple both come into play here.
--The fact that Jesus turned the water into wine doesn't negate the other NT scriptures that condemn drunkenness as a sin.
Proverbs 31 also brings into serious question the wisdom of drinking at all, lest one forget God's laws and forget how to exercise their good judgment.
--I don't believe the problem is alcohol itself as a substance, so I don't have any issue with medicines that contain alcohol or with using alcohol in cooking. The problem is imbibing and becoming intoxicated. However, if a person has a weakness for alcohol, they shouldn't have it in their home at all.
For some of the reasons above, I would have less of an issue with a person having a glass of wine at dinner at home alone than I would with "social drinking." If you feel you have the liberty to drink in moderation, at the very least choose to exercise your liberty in a way that doesn't lead others into sin (drunkenness/excess), or offend your fellow Christians. Personally, I see it as risky business.
Disclaimer: I do not believe it's wrong to take wine for communion. It's always a very small amount, there is little or no chance that anyone is going to drink enough to even become slightly intoxicated, and some people feel that it is the more "pure" way to emulate the Biblical communion ceremony. Because of the setting and obvious boundaries, I don't see what possible issues could arise, with the exception of someone being offended by the use of wine. Depending on the depth of their feelings, they could be offered grape juice instead, or the whole church can choose to use grape juice out of deference to someone who is of a weak conscience.