The SAT also doesn't measure compassion, speed or good looks. It does, however, measure something more than the ability to suck up to your high school teachers and guidance counselors.
I'd say dropping the SAT is going to have unintended consequences, except the consequences are so blindingly obvious that it's hard to pass them off as unintended. In the absence of an objective national test, Mount Holyoke will have to rely exclusively on high school transcripts, graded papers and letters of recommendation.
So instead of a color-blind, class-blind, looks-blind, personality-blind computer determining a child's entire future (as the anti-testing crowd grandiosely puts it), a student's entire future will be determined by his high school teachers.
Whatever dropping standardized tests is supposed to accomplish, it will double as affirmative action for chipper pep club members from good families with sensible clothes and nice manners. Even parents sometimes play favorites with their own children; teachers often do so blatantly. Eliminating standardized tests may be a great help to the rare smart student who doesn't test well, but it will create new unfairnesses for the smart student who doesn't play well with his teachers.
To say the SAT doesn't measure motivation is contradicted by the other claim made by SAT opponents that the results are suspect because coaching courses can improve SAT scores. If so, wouldn't taking such a class demonstrate motivation? (As for the alternative class-bias attack, it's not as if preparatory classes are in the price range of the Hope diamond, and old tests are available to anyone.)
In fact, studying for the SAT doesn't help much, anyway. According to a study of SAT preparatory courses conducted by Samuel Messick and Ann Jungeblut, 300 hours of study will lead to an average increase in combined SAT scores of only about 70 points. That's an hour a night for an entire school year plus one month of summer vacation. (For a lousy 70 points, that's motivation.)