I find the idea of people hunting up a person's social media to figure out their ethnic identity really creepy. I supremely, deeply, hate the fact that it mattered whether a contestant on the Bachelor was partly Asian, biologically.
Also, biology is not the be all end all of ethnic identity. People identify with the heritage that they identify with for many reasons. I know someone who is second generation Mexican American on her father's side technically, but does not identify with that culture at all because she was raised in a white household her entire life. She speaks no Spanish,