That's one of the main reasons why I'm dropping everything and moving to San Francisco in about a week to work on my startup. As much as I like Chicago, the connections and resources just aren't there yet.
For those of you actually interested in events in the Midwest, I can tell you that we're doing some interesting things in Cleveland that I can scrounge up more information about. Nothing conference-level that I'm aware of, but events with founders and incubators are becoming more and more frequent.
Edit: Cleveland Startup Weekend is in November and there's some sort of kickoff party in a few days. http://cleveland.startupweekend.org/
The Midwest won't have a successful Startup School clone (at least not with speakers of this caliber) because it's not dense enough with startup people. Maybe there are enough people to make the event worthwhile in all of the Midwest, but it's such a huge area that a lot of people would still be facing very long drives or flying.
When people say "I want an event like this in <my region>", they really mean "I want an event like this within a 2 hour drive of my house, preferably closer." They don't mean "I live in Ohio and would happily travel to Kansas for this event." If someone were to announce an event like this in, say, Minneapolis, a lot of people form Indiana and Ohio would realize that that's not what they had in mind when they asked for a Startup School clone in the Midwest.
And now PG's invested in a flight comparison startup, so just as people sometimes link to http://www.justfuckinggoogleit.com/, he can link to Hipmunk to say "just fucking fly here."
Even if the answer is as simple "YC's plate is totally full just keeping up with the SV scene" or "pg hates the cold", that would be more compelling than just a brush off and link to some plane tickets.
If you want a different opinion, read 37signals' blog and books. They're right there in Chicago.
"Why does Silicon Valley ignore the Midwest" strikes me as missing the point entirely. Regions don't become entrepreneurial by the careful attention of people from other, more entrepreneurial regions. They do it themselves. That is the point of entrepreneurship!