There's been another debate in the blog-o-sphere, started by something Ryan Dancy said about social mechanics, which I've been loosely following. I'm not going to link to all I've read, because most of you have seen it anyway; those who haven't can use Trollsmyth's post as a good place to start.
I haven't said much about it because I've already said a lot about social mechanics, posted a few suggestions of my own, but mostly focused on the point that whether or not you are using a die roll or role-playing it out is irrelevant; the decision on whether a character's argument is effective has nothing to do with how the player speaks, but what the player says. A fair GM will listen to the player's key points and decide how the ideas affect the target's reaction.
I also have to point out that the old-school reaction roll, in contrast to the new-school Diplomacy, Fast Talk, or Intimidation skills, is not a skill roll; the GM is not rolling to see if the character's performance is successful, but rather rolling to see what the target's behavior is going to be. An NPC might actually find a character's argument extremely persuasive -- but still do basically what they were planning all along.
I can't see adding social mechanics just so you can determine "who wins", because that has to be a judgment based on the situation. Some creatures are always hostile, or hostile to particular species or in specific situations. Others might be more variable. Some will have specific reactions based on a character's Charisma (the dryad being an example of this.) You can't force this into an all-in-one social mechanic.
On the other hand, I can see adding social mechanics to add detail to "what happens". A couple times, I suggested using the straight-up D&D combat rules for social combat. This would only be useful in arena-like situations (a criminal trial, verbal sparring at a party) or when time is important (can you convince the mastermind to give up his evil plan before the bomb is activated?) You aren't rolling to take control of another character; you're rolling to see if witnesses would agree that you won that argument.
It's a subtle difference, but a big one.