@websensation yup. pretty much agree with your points as well. especially about the kid who tries to use a sudden found passion as an ameliorating factor for bad grades. that is just bogus.
on your other question, it is typically very very hard if not impossible to switch to an engineering major midstream at highly ranked colleges. switching within humanities is quite easy. sometimes switching to business is also tough - like at UCB Haas. But not as impossible as suddenly deciding to be an engineer.