If there's an actual blacklist where YC employees can just arbitrarily ban founders from working with certain companies that's quite surprising and maybe pretty bad for YC's reputation.
If you mean YC has a strong community of founders who share war stories of how people and companies were difficult to work with, and the other YC founders pay attention to those stories though, well, that's not a blacklist.
If you mean YC has a strong community of founders who share war stories of how people and companies were difficult to work with, and the other YC founders pay attention to those stories though, well, that's not a blacklist.