Anything that good hackers would find interesting. [...] anything that gratifies one's intellectual curiosity.
I was at PyCon as well, and observed the exact same anecdote that the OP describes. At my company's booth, the only minorities I can think of who talked to us were more than likely visiting from Europe, Asia, or South America. Therefore, I'm curious, and I'm interested to see the response; not from accusing Y Combinator of racism, as some seem to suggest, but merely to get some data on minority penetration into our field.
There is no "standard" for the front page. We're all smart people, and we can be trusted to make judgments.