1. All people are entitled to sing a song once in a while.
2. In a public social atmosphere, all people are obligated to be aware of their surroundings.
3. If the karaoke is a free service provided in a bar, you are obligated to get a drink if you want to participate in the free service.
4. Time is finite and songs take up time. If you don't get to sing a song because of the queue being particularly long, the proper attitude is, "Well hey, at least I'm still not involved in a civil war in Central Africa."