highforthis saidI see tons of clearly-black or asian guys claiming to be "mixed race". Presumably this is the same reason others put "29" or "39" under age, to avoid elimination in searches. I actually don't mind the ones who admit to trying to cheat the system, but get kinda annoyed by the few who insist on their 1/8th British heritage, or some other BS. . Will you date them?
Many black americans are in fact of tri-racial (native, european and African) origins. The state I live in, has the fourth largest native american population in the country but a large tribe known as the Lumbee are not completely recognized as Native Americans despite maintaining their tradition and identifying as such. They are in fact a tri-racial tribe. I often mistake them for being Latin American until I hear a deep country drawl when they speak.
I dated a guy once and had no idea he was black when I first met him until he referred to himself as such. I thought he was mixed-race and in fact he is again tri-racial. He looked like he could have been related to my Venezuelan friend. The latter's father identified as black but his white Spanish mother just simply raised her kids as Venezuelans and he would never say his is black though he has told me his father is.
So if someone with brown skin says he is mixed race, he probably is. And if you get annoyed that they aren't screaming out "warning my skin is dark enough to pass for African", then maybe you have a problem.