^ I will only be impressed with someone who starts playing guitar in a social situation if they own a quadruple neck and shred like the always hilarious Michael Angelo Batio
Picture it. You, some friends, some assorted alcoholic beverages and some general good times. Lovely. Hey, look! One of the people in your group has suddenly cracked out an acoustic guitar. Oh. Fiddlesticks.
There are several problems with doing this. Firstly, nothing says "Lavish me with attention, I'm so desperate for social validation right now" like feebly trying to show off your "creative skills" in a group situation. It forces everyone else to stop what they are doing and pay attention to you - especially if you begin to warble over the top of your badly strung together chords. At least if you were just quietly noodling in the background, you could maintain the façade that you were providing instrumental accompaniment to the evening's proceedings - like a low-budget pianist in a not-so-fancy restaurant. But with you caterwauling about some non-profound, pretentious insight over the top of your generic chord progression, you prevent everyone else around you from enjoying their evening.
The only thing that could possibly make this worse is if you try to get your victims to sing along. Not only have you ruined their previous activity of casual socialising and alcohol, you are now forcing them to pretend they know the words to every bland and overplayed song you can think of; from the vomit of Oasis and appalling Bob Dylan covers to the tripe of whatever indie nonsense passes off as music nowadays. You are not talented and never will be. Sod off.