In order to do things that are out of your comfort zone you need to have been with someone long enough to know that they can be trusted to back off when they are asked. However, when people are really drunk, I think that is when things go to far. Sometime people go to dark places when they are drinking. (Pot is different--I think that drug can actually bring out people's gentler natures.)
That being said, once you have been in a relationship a while, doing things out of your comfort zone is an act of love and you may enjoy it.