Where the hell is the response to this I posted...?

Erm...I was basically saying you had a good point, and that the nepotism we see is very much like the nepotism you're describing in the real world. Especially given that the Purebloods are supposed to all be related--no wonder they see anyone who looks outside them as being a threat.

I love in canon when we're introduced to some random person with their own history--like Ernie MacMillan talking about how his family is Pureblood for X generations and big supporters of Dumbledore. Everybody's got a history!