What do you think are things that are barriers to relationships and/or "cock blockers"? For example If a woman has a man for a friend that she hangs out with is that a barrier to them finding a relationship with someone else? If someone has a FWB/playmate....is that something that will block their ability to create a relationship with someone else? If a white woman is hanging out with a Black woman/women does is that a barrier to Black men approaching her? What if it's a Black man hanging out with white friends? What are things that make a woman or a man not approachable? Feel free to answer these questions and bring up others that would relate.
At the end of the day, it's about what we, as human beings, like or dislike. I wouldn't use the term "cock block" since it is a sexual reference. We all have certain preferences when it comes to people and things.
I think most of these would be insecure people in one way or another, especially where the person has a friend of the opposite gender. Steve Harvey often says that backward crap that a platonic friendship between genders aren't possible because supposedly one of the two (usally the guy) is simply "waiting for an opportunity. Things for me that make a woman unapproachable would include offensive stuff. Like if she has an allegiance to hate groups, and the like. This list could go on forever, but also things like her own personal appearance and values. I'd bet plenty that some BM get considered off limits to some if he has white friends. I had someone ask about one of my friends because he was once married to an Asian women, he has plenty of Asian friends. The person's exact words were... "He's good looking, but what his deal with all of these friends of different hues".