Here's my take on jukebox etiquette: bars have a vibe about them, and you need to respect that vibe by not putting on music that clashes with it. Additionally, (and I can't emphasize this enough):
1.) You HAVE TO not hoard the machine.
2.) You CAN'T put on more music than the time you're going to be there
Case in point: about two weeks ago my old roommate and I wanted to shoot some pool, so we went down to this bar with a couple of pool tables in it to have a few and shoot some stick. The jukebox there was one of those internet ones where $1 gets you two credits and each song is 1 credit (2 if it doesn't have it on the box and have to download it from the internet; 2.50 if yuo want it to preempt the others). Now, this bar is in the basement of an old building, it's dark, smokey . . . basically, it's not the kind of place you take someone out for drinks on a date. And, I mean, this kind of bar is the kind I love. Anyway, we sit down to grab a drink, and we start shooting some pool, and we were just going to go with whatever was being played (since, when we came in, they were playing some Lynyrd Skynyrd), when suddenly we see these two girls in tie-dyed shirts sit down by the jukebox and start feeding money in. We think nothing of it, until we hear what they put on. It was techno, VERY loud techno, VERY VERY bad techno. I mean, I'm not crazy about techno in general, but I can listen to it in passing now and again, and I accept it being played at trendy clubs I go to and whatnot. But at this bar? No way. So I grimace a little and keep playing, thinking it's just a song or two. But once it hits the third or fourth song, and the two lesbians at the table over and my buddy and I are all kind of looking at each other thinking "What the hell?", I start to go over there to change it and put some songs in, thinking it has to end soon. As I go over there and select my songs, I look at the playlist queued, and realize that they put in enough money for TEN techno songs. I wasn't about to preempt them (since they'd play anyway, and I couldn't afford that kind of cash), so I went back and reported to the other three how crappy that was. But that wasn't the straw that broke the camel's back; what did it was that one song later THEY LEFT, leaving us to have to listen to the remainder of that crap. Thankfully, the bartender took mercy, pulled the power on the box, and then replaced the $3 or so I put in so I could re-input my songs. But I wanted to kill those girls.