I do not believe every person is open to the idea of open relationships, but I do believe there are people who are. I think being part of an open relationship can be a very easy decision for people who chose to focus more on other life events or careers.
Although we, as a society, are becoming increasingly liberal, open relationships are still somewhat taboo. The recent issues regarding same sex marriage emphasize that a large part of society still maintains a one man and one woman mentality. Anything that falls outside of this mentality is regarded by individuals with this mindset as sexually deviant.