As many of you (I hope?) noted, I'm working on a homebrew system that's meant to be extremely pick-up and play, and the majority of the rules are in regard to physical effects.
Up 'til now, I've eschewed putting in a social combat system because... frankly, I'm kind of ambivalent about them in general.
All of the ones I've seen tend to be extremely ad-hoc in play; any GM who sees something as a reasonable statement grants you a circumstance/equipment/whatever bonus or says it works or whatnot and what have you.
The best I've seen are systems that said "well, you say this and the GM decides it was good and therefore knocked off this much of the person's resolve" (which is determined in ad-hoc by the GM) "so you succeed!" Which is barely one step above free-form.
I can see a social combat system working well in a very complicated, rules-heavy game where everything is defined and metered. (It would have to be done -very- well, though.) But in a rules-light game, is there even a point?