well.. from my experience, id gotta to say that in general most guitarists are really uptight about this sort of thing. a good number of my friends play guitar and they bitch excessively whenever i fiddle with it.
unless your friend fiddling with your guitar is stupid or has been known to break lots of stuff, then i wouldnt worry about it that much. the strings are made of steel you know :p. but i can totally understand why youd be protective though. a guitar is expensive.
one time i did rape my friends guitar though. i leaned it against an amp and it fell on the pavement. :D

Seriously, has anyone heard of Sonic Youth? They **** up their guitars and still sound good.

sonic youth also collected their guitars at pawn shops at a time when their models of choice were basically being given away.

it's a lot easier on your conscience to make a homemade 3rd bridge guitar with something you picked up for $150 rather than $1500.

I thought that Lee and Thurston just played behind the bridge of a jazzmaster to get the sound of chiming bells.

depends on the tune. the chiming bell effect isn't going to hurt anything. the 3rd bridge setup is usually created by shoving a screwdriver or butter knife between the strings and the fretboard around the lower frets.

I hated it when a kid I jammed with (great guitarist) would bang the body here and there when changing amp settings and stuff. I told him to stop repeatedly, but he would still do it occasionally.

As long as whoever plays my guitar cares for it, I'm fine with them playing it, but I never hand it out blindly. I'd stow it away or tell people not to bother with it (if they ask why I usually just say something's wrong with it and it needs fixing).

My brother bought a ****ty guitar just for other ppl to play so they won't touch his Strat...I play the drums...I have a Pearl Export series drum set with Sabian series B cymbals and I let ppl just bang away on them...Well, if by ppl I mean hot chicks:-)

Damn friends always pickin up my guitar and throwin it around, its a Damn les paul have some ****ing respect for it, they throw it on the bed and the knobs are going flat and it messes up the tuning and AAHHHH it pisses me off.

Lol, thats when you go behind them, and hold there hands while they have the drum sticks in em, and show her how to play the drums, then the fun comes ;) lol

One of my guitars was brutally raped by a friend of mine a few years back.. She was acting like a dumbass, tripped, knocked it over, and then fell on top of it.. snapping the head off. I promptly grabbed her skateboard and smashed it. I managed to fix the guitar but it doesn't play quite the same. Wasn't an amazing guitar anyways but damn.. show some respect.