I appreciate Brilliant.org because it is egalitarian, inexpensive, accessible globally, breaks down barriers to the spread of knowledge, and fosters a culture of sharing.
The Stanford High Summer Program is, of course, quite useful for those who attend it. It is, however, the epitome of a number of things wrong with the current education system: they are elitist, meant for the privileged few, geograhically limited, and expensive.
I would like to believe that Brilliant.org's valuable time / money / resources would be far better spent in addressing the issue of how to spread around education more whether via a MOOC or via internally created MOOCs than to plug an expensive local solution to a global problem.
Why dont you guys create your own program (or invite someone for it), with videos and forums accessible to everyone, and mentoring for a select few who are academically gifted, and committed to participating.